Distribution and Ecology of Certain Japanese Rhododendrons:
A Progress Report
Frank Doleshy, Seattle, Wash.
All republication rights reserved by the author.
In 1967 as in 1965, Mrs. Doleshy and I traveled mainly in those areas of Japan where there are Rhododendrons of the Ponticum group. The number of distinct species in this group is a matter of interpretation, but most authorities of the present day recognize four in Japan:
. Also, especially in the case of
, several varieties are distinguished.
The question of legitimate names has been discussed in previous issues of this Bulletin (July, 1966 and January, 1968), and we leave it to the reader to determine his own preferences. We use the names of Ohwi's Flora of Japan , but we hardly expect these modern names to sweep away the old nomenclature overnight, either in private conversation or on nursery labels. Indeed, only a brave nurseryman would, today, re-label his precious stock of "yakushimanum" as R. metternichii var. yakushimanum . We sympathize, but are not so sympathetic that we want to ignore the excellent work done by Japanese and other botanists during the last 40 years.
The current names will perhaps seem less formidable if they are sorted out geographically. Looking first at the R. metternichii-R. makinoi complex, a fairly clear line of distinction can be drawn between the plants which inhabit the "Outer Ring" and those which inhabit the "Inner Area", as shown in Fig. 36. The Outer Ring plants have rather closely-spaced leaves with heavy indumentum. Starting from the north, the first is R. metternichii var. pentamerum . Next is the narrow-leaved R. makinoi , occupying a very small area. After a gap, R. metternichii var. metternichii is first encountered on the Kii Peninsula and Shikoku and is then found in many mountain areas of Kyuūshū. Finally R. metternichii var. yakushimanum grows on the three high peaks of Yakushima and, except for indumentum on stems and seed capsules, is amazingly similar to the far-north var. pentamerum .
The Inner Area contains a phase of R. metternichii which usually grows to a larger size, with more open habit and thinner indumentum, although these differences are not always very clear cut. Until recently, many authorities lumped these Inner Area plants together as R. metternichii var. hondoense , the common large-leaved Rhododendron of S. W. Honshū and part of Shikoku. This is generally a plant with 7 part flowers, and a problem arose because populations with 5-part flowers were known to exist in an area generally west of Tōkyō. Based on type material collected in 1961, Takasi Yamazaki, of the University of Tōkyō, described these in 1964 as R. metternichii var. kyomaruense (Journal of Japanese Botany, 39:1, pp. 13-18). However, the distinctness of these plants was earlier recognized by Mr. K. Wada, owner of the Hakoneya Nurseries in Yokohama, and he has cataloged and distributed them for at least 30 years as R. metternianum . Therefore, under the rules for priority of name, it appears that this latter name is valid.
And, if we adopt the view that these plants are varieties of R. metternichii , the name becomes R. metternichii var. metternianum (Wada). For further discussion see note at the end of this Report.
|Fig. 36. Distribution of certain Rhododendron species in Japan.|
Another of the maps in Fig. 36 shows the general distribution of
. This blankets the area of
, extends much farther north, and also grows in Korea. In addition, there is some overlap of this species into the territory of
, and we understand that there is an interesting occurrence on the two high mountains of Shikoku. Also, we have heard the serious suggestion that a population may exist on Yakushima, and we are very curious about a group of plants which I failed to approach closely in 1965.
is a large open growing plant except where dwarfed by extreme climatic conditions, and the leaves may have a thin indumentum or no indumentum at all. Superficial resemblance between
and the Inner Area
is interesting but not necessarily meaningful.
The fourth species, R. aureum , is known to many as R. chrysanthum , an invalid name which was unfortunately popularized as a result of incomplete research. We have not yet given much attention to this plant and therefore do not include a map. Generally, its range extends northward from the high mountains of central Honshū through Hokkaido and into Siberia. When examining dried material in the Harvard University Herbaria we particularly noticed the rich yellow color (or, at least, the durability of this color) in flowers from Siberia. New introductions from that part of its range may be of interest.
Considering now the major geographical boundaries of Japan (also shown in Fig. 36), there are obvious tendencies toward correlation with Rhododendron distribution. The Fossa Magna, or "great trench", is the place where Japan is virtually broken in two, with younger rocks to the north and older rocks to the southwest. The cliffs of the west scarp, rising from the floor of the trench, provide spectacular views from equally spectacular roads. However, much of the trench has been filled in by volcanoes, including Mt. Fuji, the tallest mountain in Japan, and the Yatsugatake Range farther north.
The Median Dislocation is not everywhere such a scenic feature as the Fossa Magna and is most impressive on the geological maps. To the north there is much igneous rock, both volcanic and granitic, and the area to the south consists of zone after zone of sedimentary and metamorphic rocks: sandstone, shale, slate, limestone, chert, etc., with occasional granitic intrusions and a large volcanic area in southern Kyūshū.
R. metternichii var. pentamerum occurs to the north of the Fossa Magna and R. metternichii var. hondoense to the southwest; R. makinoi is in a small area near the Median Dislocation, and R. metternichii var. metternianum occupies certain areas in an arc which straddles both the Fossa Magna and the Median Dislocation.
With this as background, we selected our objectives for 1967. First, we wanted to see if the extremely narrow-leaved characteristic of R. makinoi extended along the Median Dislocation to the northeast of the known range of this plant. Second, we had gladly accepted when Mr. Wada suggested that he arrange a guided trip to a remote population of R. metternichii var. metternianum . Third, we hoped to find an area where R. metternichii var pentamerum and var. hondoense could be observed and compared in close proximity, on their respective sides of the Fossa Magna. Finally, we were extremely curious about the characteristics of R. metternichii var. metternichii at the southern limit of its range, in Kyūshū.
Our success in meeting these objectives was variable, and we often had to be satisfied with negative results (i.e., "No Rhododendrons to be found on that ***** mountain.") But these disappointments were offset by finding an unexpected correlation between the presence of Rhododendrons and the character of the rock at their roots. This is perhaps common knowledge in Japan and should not have been such a surprise to us, since we had previously observed that the American R. macrophyllum occurs on certain types of glacial outwash soil but not on others. (See January, 1963 issue of this Bulletin , pp. 3-8.)
Fig. 37. Prefectures visited for Rhododendrons
Arriving in Tōkyō, we were met by Mr. Warren Berg, of Kent, Wash. He was hurrying to pilot his airplane to Seattle but paused to tell us to phone Mr. Wada immediately about our plans for the first two days. Mr. Wada had written to us about a trip to the Izu Peninsula to look at one population of
. But, because of bad weather, he decided to substitute an interesting visit to the Rhododendron garden of his friend, Mr. Enomoto, an expert on Rhododendrons in the wild. From there we went to Mr. Wada's 5-acre ridge top nursery in Yokohama and then to his beautiful home for the night. Here, the other evening guest was Mr. T. Takeuchi, of Kawasaki, another member of our Society and a very knowledgeable seed collector. Both he and Mr. Wada were so generous with their hard-won information that we could have spent much more than our 6 weeks on the areas they told us about.
Next morning the Wadas drove us to the station to board the Bullet Train for Shizuoka. There, we left the usual path of foreign tourists and took a mountain bus to Sumatakyo Spa, in the Akaishi Mountains. Sumatakyo is just east of the Median Dislocation, in the locality where this line curves up to meet the Fossa Magna, and we expected to find fairly plentiful R. metternichii , possibly showing some eastward trace of influence from R. makinoi . However, Rhododendrons are hardly profuse in this area; going to the lobby of our inn after dinner to talk with the staff and other guests, we learned that there was one population within striking distance, 5 kilometers away on a straight line but actually to be reached by following a logging railway for several kilometers, dropping down to a dam, and climbing the ridge behind. Much rather well-informed advice was offered by the boisterous crowd of guests, clad in kimonos like ours. They turned out to be the members of a firm of consulting chemical engineers, enjoying a holiday. One of them was a University of Washington Ph.D. but couldn't sing our old school song in Japanese any better than I could. Meanwhile the inn's manager drew us a map and arranged for the dam-tender to leave his generator controls for a few hours and show us how to go up the ridge to the Rhododendrons.
The next morning, however, the manager had decided to go with us and was able to arrange a ride to the dam via logging train. On the east side of the ridge, just below the crest, we reached the surprisingly small Rhododendron population, perhaps 300 meters across and 100 meters up and down the slope. These were growing and regenerating vigorously among trees on humus soil, and plants of all sizes could be seen. The largest ones had slanting main stems 3-3½ m. long and as much as 13 cm. in diameter. Their open habit and thin, light-colored indumentum stamped them as "Inner Area" R. metternichii , i.e., members of the complex which consists of vars. hondoense and metternianum . However, the metallic sheen of the indumentum was as attractive as on the much-praised R. insigne , and the large and numerous seed capsules indicated free flowering. We collected herbarium material and seed as No. 21, initially listed as "var. hondoense or natural intermediate with var. kyomaruense . But, as mentioned above, we now believe that kyomaruense is not the legitimate name and therefore want to correct this listing to read, "var. hondoense or natural intermediate with var. metternianum ."
These were evidently the only known wild Rhododendrons within a very rugged area of 5-6 km. radius surrounding Sumatakyo Spa. Growing at an elevation of 1100 m., they were 500 m. higher than the R. makinoi which we had seen in 1965, about 45 km. away. But no trace of the narrow leaved R. makinoi character could be seen here, and it seems possible that the latter species occupies its limited habitat as a relic population.
The next day we traveled by bus, private railway, Japanese National Railway express train, JNR bus, and taxi to reach Chubu Tenryū, a town in the next major watershed. Arriving in time for late bath and dinner, we found ourselves only 30½ km. west of the Sumatakyo inn which we had left at 9:00 AM. Moreover, we were there to see a plant population only 12½ km. from our collecting place of the day before. "Why didn't we walk?", some have asked-and this would have been attractive if we had known some way to float our suitcases over the ridges and valleys that separate the two towns.
Catching a 7:52 train the next morning, we rode mainly through tunnels for 17 minutes and got off at Mukaichiba Station. As arranged by Mr. Wada, we were met there by Mr. T. Amano, good-natured climbing companion and fellow plant collector, and our destination was Jōkoji Mountain, home of the Rhododendron population from which Yamazaki took his type specimen of R. metternichii var. kyomaruense (which we call var. metternianum ). The first 4 km. were covered rapidly, by taxi, but we then had to start up the trail. A postman with a knapsack of mail on his back walked with us to Yamazumi Shrine, on the first ridge-crest. Here, in a grove of Cryptomerias as big as California redwoods, we had tea with the priest and looked at a transplanted specimen of the Rhododendron. Continuing via the ridge, we worked our way up to the main mass of the mountain, noting with interest the numerous kinds of Azaleas and also the reforested cedar trees which had been badly damaged by bears gnawing for sweet sap. After crossing the shoulder of Jōkoji at 1200 m. we clambered down a steep, unstable slope of fractured red rock, following the deer trails in order to keep our footing. At about 1000 m. elevation we turned left onto a ridge of whitish rock and continued down, soon seeing a few specimens of our quarry. They were most numerous at about 900 m., growing on matted humus which covered the more gentle parts of the ridge. A majority of the plants were in about 65% shade and as erect as young conifers, with an average height of 3½-4 m. On these the leaves and trusses were at the top, but plants in occasional open spots had quite dense foliage down to ground level. Leaves and habit were very similar to No. 21, except that the indumentum was thinner-hardly more than a pale-buff coloration. But they seemed even more floriferous, and we found that the trusses usually consisted of 7-12 seed capsules (average, about 10). These we collected as our No. 22 with the help of Mr. Amano, who was also collecting for Mr. Wada.
Mr. Amano indicated that this sub-population covered an area about 300 m. in diameter and that there were two other similar sub-populations within 1 km., on the same north slope.
Samples of rock from under the roots are porcelain-like, with a fine network of cracks and thin veins of clear material. This rock is a chert, consisting of nearly pure silica, and the cracked texture probably resulted from extreme stress. This type of rock, in certain color forms, is commonly called flint or jasper, and its hard, tough character is well known.
Our return completed a great, circular tour, and at 4:30 P. M we were on the 1439 m. summit of Jōkoji, looking across a valley to the shrine we had visited in the morning. From here the giant Cryptomerias could be seen, but only as tiny projections from the ridge. Just at dark, we reached Mr. Amano's mountain-side tobacco farm and reluctantly declined Mrs. Amano's invitation to dinner. Our inn, we knew, would be waiting for us with concern, so we contented ourselves with milk and rolls, walked down the trail by flashlight for another hour to reach the end of the road, took a taxi to the station, and caught the 7:33 train to Chūbu Tenryū. There, we walked across town to our inn, and vacationers taking late-evening strolls looked at us rather askance since we obviously had not yet had bath and dinner, but we soon took care of these things.
On this entire day of hiking and climbing, mostly above the 900 m. elevation of our collecting area, we saw not a single other wild plant of the Ponticum-group Rhododendrons. The lesson was becoming clear to us: Except in a few areas of Japan, the Rhododendron hunter cannot hope to succeed by merely heading for the nearest mountain with collecting bags and notebook.
The Geological Center of Japan
From Chūbu Tenryū we took a train north along the remaining length of the Median Dislocation to its intersection with the Fossa Magna, at Lake Suwa. We thought that this mountain-ringed lake at an elevation of 759 m. would be a splendid center for touring out in all directions to see the various phases of
, and we became familiar customers at the railway and bus stations. But we saw no
at all in the Suwa area.
What were we missing? We appeared to be within the proper range of elevations, on slopes with the favored east-north-west exposures, and on soils which came within the wide range of tolerance. But, wherever we had seen Rhododendrons in other localities, the soil was thin, and the roots were never far from the rock. Perhaps we were not giving enough attention to the nature of this rock - although we had noticed an apparent preference for a particular type of rock at Jōkoji Mountain.
Another and more striking example was seen near Lake Suwa. Even though we found no R. metternichii in this area we did see R. brachycarpum . This latter species (our No. 28) was growing at Yokodake in the Yatsugatake Range. At the high elevation of 2:300 m. these plants were dwarfed and, interestingly, had no indumentum. Put the amazing thing was their preference for a fresh-looking lava flow which looked like dark brown clinkers. Here the plants were growing everywhere, but we saw none beyond the abrupt edge of this particular lava flow. Indeed, when we crossed over to the light-colored rock and the soils derived from other eruptions, the flora was entirely different; ericaceous plants were replaced by grass and bamboo, rippling in the cold wind.
The lava favored by the Rhododendrons had a high content of iron-magnesium minerals. However, the surrounding light-colored fine-grained volcanic were probably similar to granite in chemical composition - and granite supports Rhododendrons on Yakushima and elsewhere. Therefore it appeared that the open, porous texture of the clinker-like lava (an andesite scoria) was the important factor.
With this in mind, we spent the next day at the top of the great west scarp of the Fossa Magna and walked over several kilometers of the old sedimentary rocks (sandstone, shale, chert, limestone, etc.) which occur here. We saw neither R. metternichii nor R. brachycarpum , although we now think that one or the other might have been found by following chert ridges to points where exposure and shade were favorable. Our collections were R. japonicum (Nos. 26 and 27) plus some very attractive Acer micranthum .
Return to Kyūshū
We next took a vacation within a vacation, buying dishes in Nagoya, touring the scenery of the north coast of Honshū, and crossing to our favorite island of Kyūshū at 100 km. per hour on the train named Yaegaki, in a tunnel deep under the sea. On Kyūshū we promptly went to Kurume to meet with Mr. Kunishige, of the Horticultural Research Station. Recently, this gentleman had worked with Dr. Creech for a year at Beltsville, Maryland, and Dr. Creech had suggested that it would be foolish to venture into central Kyūshū without stopping for his advice.
Kurume is tire-town and Azaleatown. Perhaps unjustifiably, we ignored the former, having spent the previous afternoon at Yahata Iron and Steel Plant No. 2, seeing how steel will be made in other progressive nations by the end of the Twentieth Century. But the collections and experimental plantings of Azaleas at the Research Station were like nothing we had ever seen before. We learned, among other things, of the pink-throated Unzen phase of R. kiusianum , and we saw large specimens of R. sataense which convinced us that this somewhat controversial plant is clearly distinct from R. kiusianum . Also we looked with interest at R. metternichii var. yakushimanum from seed collected by Mr. Kunishige on Nagata-dake, at the N.W. corner of the Yakushima mountain mass. These appeared the same as similar-size plants from seed collected on Miyanoura-dake and Kuromi-dake.
Although Mr. Kunishige is probably the prime expert on Kyūshū Azaleas, he modestly disclaimed any major knowledge of the Ponticum-group Rhododendrons and had called in a commercial nurseryman with years of collecting experience. The tea cups were soon covered with road and contour maps, and the two hours of Japanese and English conversation turned into a friendly free-for-all, ranging from wild speculation to the solid evidence of field observations. Unfortunately, at that time, we had not yet been able to obtain geological maps showing the rock formations of Kyūshū, and we did not realize until later what a disadvantage this was - both with respect to finding plants and interpreting our observations. However, the Kurume people gave us so many specific directions that we could only utilize a few on this trip, and they also warned that our far-south search for R. metternichii would be difficult and perhaps unsuccessful.
Leaving the next morning we went first to the offshore island of Fukueshima, flying out through the advancing edge of Typhoon No. 34. Here we enjoyed a minor victory; our Japanese friends tended to laugh this off as an expedition to go and eat some of the incomparable food served on the small islands around Kyūshū, and they were partly right. But we did find an Azalea, possibly R. weyrichii (No. 32), and immediately mailed seed to several addresses in Japan.
We returned to serious pursuit of R. metternichii in the volcanic area of N. Kyūshū, an arm of the Inland Sea in the geological past but subsequently filled with enormous flows of andesite lava. Our base was Hita, and we followed the advice of the Kurume nurseryman, who stated that the Rhododendrons on the mountains south of Hita had flowers of deeper color than those on Mt. Hiko and other peaks to the north. By bus we traveled 12½ km. south to Ono then walked 6 or 7 km. to reach the eastern peak of Shakutake. This was composed of fractured but close-grained lava, very light in color, and supported a fairly rich flora but no Ponticum-group Rhododendrons (and we had seen none on the entire trip up). The west peak, of approximately equal elevation, was only about 200 m. distant and reached in a few minutes. Here the rock was much different; gray and subgranular. And the shrub vegetation extending around the east, north and west sides of this peak consisted almost entirely of R. metternichii var. metternichii .
Two weeks later, when we finally obtained the geological maps in Tokyo, the situation became clear. The two twin peaks straddle a probable fault of major extent, the andesite lava of the east peak was laid down in the relatively recent Quaternary Period, and that of the west peak dates from the more remote Tertiary. Apparently the longer interval of erosion has exposed a more slowly-cooled lava at the west peak, and this has a porous texture which contrasts sharply with the tight surface of the east peak.
R. metternichii var. metternichii
Up to this point we had walked with a law student from Fukuoka University, swapping tall tales about Mt. Rainier and the Yakushima climbs, and he left us here, disappointed at our sudden change of interests. We had never before seen this variety of
in the wild and had much to look at. Although the leaves of this particular population had a mat surface the color was deep, clear green, somewhat whitened by residue of top-surface indumentum, and the moderately domed and recurved shape of the leaves reminded us of the far-north and Yakushima phases of this species. The plants were vigorous and slanted out from the slope, with main stems up to 3 m. long and 12 cm. in diameter. Lower-surface indumentum was thick and a medium buff color. The observed number of capsules per truss ranged from 4 to 9, but most or all of these trusses were incomplete, and it was difficult to tell how many capsules had dropped off. This seed is our No. 35.
The Rhododendron belt on this peak was possibly 25-30 m. up and down, with a central elevation of 1210 m., and extended around the peak for a distance of about 100 m. We did not have time to go on to other peaks which formed a ridge to the west, although the Kurume nurseryman had indicated that additional groups of Rhododendrons extended 1½ km. to Gonzendake, at the west end of the ridge. Also, somewhere on this ridge, he had found an albino with spotless, pure-white flowers and was propagating this but could not maintain an unsold stock. We hope to obtain one of these when available.
Next we went to Beppu, saw R. kiusianum (No. 37) on Mt. Tsurumi, and picked up our U-drive Toyota. We had neglected to obtain checkered fast caps and white-string gloves but were able to give other drivers the proper hand wave as we left the inn's parking area. Our destination was the main north-south divide of Kyūshū, a prime objective since October 20, 1965, when a Kumamoto hotel manager had given us a tourist booklet indicating some kind of road down the middle of Kyūshū. For nearly two years this road was a major preoccupation; did it exist or was it merely a theory? The travel agencies insisted that no bus ran there (and they were so right). Also, the maps from the car-rental agencies showed no such road. But, in September, 1967, Mr. Kunishige surprised us by sending the most welcome gift we have ever received - a large and excellent road map of Kyūshū. This showed National Road 265 running north and south, as close as possible to the main divide. So we confirmed our car rental arrangements and redoubled our respective efforts with written and spoken Japanese (desirable for any serious traveler; practically essential when it is going to be necessary to ask driving directions and keep a car serviced).
Now, from Beppu, we were starting toward NR 265, via the magnificent northern cross-Kyūshū highway. Our first stop was Mimatayama, at 1300 m. in the Mt. Kuju complex. This had been recommended as the site of excellent R. metternichii var. metternichii by Mr. Wada and his friends, also by the people at Kurume.
Although the geological map shows this entire area as relatively new andesite lava, the one Rhododendron-filled gulley was floored with different material: boulders of granular rock containing much biotite mica. This small area is perhaps the summit of an old granite island, not quite engulfed by the lava flows, or more likely re-exposed by erosion of the lava.
The largest of these boulders were about the size of automobiles, and they rose from a ground level which was simply a compact layer of smaller boulders. The rock surfaces were covered with moss and lichens, and Rhododendrons of all sizes grew in this coating or in small pockets of humus on the tops of the rocks. Year-old seedlings barely topped the moss, but mature plants had main stems to 3 m. long. And, surprisingly, the roots of these large plants had crept down the sides of the rocks, under the moss, for distances of 2 m. and more to reach the ground level.
This was the source of our No. 38, obviously a worth-while population, with very smooth and shiny deep-green leaves, generally a little narrower than those of No. 35. Vestiges of top-surface tomentum were confined to petiole and midrib groove, but undersurface indumentum was dense and variable in color: pale buff on current year's leaves, bright orange on last year's leaves, and a dull, darker color on 3 and 4 year old leaves. Some trusses appeared to be complete, with an average of about 10 capsules.
Further south, at Mt. Aso, we left the high-speed road network and were delighted when we found the right turn out of Takamori and saw a NR 265 marker. Here the road was not bad; steep and narrow but maintained for substantial car and truck traffic. Several kilometers south of Aso, near the Ōita-Miyazaki Prefectural boundary, we crossed the Median Dislocation and entered the folded mountains of central Kyūshū, a broad zone of the same sedimentary and metamorphic formations that we had seen at Sumatakyo and Jōkoji Mountain, almost 700 km. away in Honshū.
The distribution maps show R. metternichii at scattered locations in this part of Kyūshū, and we had hoped to see an interesting sequence of populations as we drove south toward our main objective, Mt. Ichibusa. However, this plant is probably confined to certain areas of favorable rock, and we saw none en route. During our second day of travel we were often misled by thickets of Camellia and stopped the car to dash out for a close look. This created no traffic problem in the remote central passes because no other automobile had crossed that day, but the lack of traffic was not entirely an advantage; we had to stop several times to roll large rocks off the road, and these had to go to the uphill side because we didn't want to push them over the edge and demolish a log truck operating on a road 500 m. below. Also there were some pedestrians - neatly starched school girls apparently walking from nowhere to nowhere and always ready to wave with surprise at a car with Ōita license plates in the middle of Miyazaki.
Mt. Ichibusa, 1722 m. high, was the place we had chosen to look for far southern
, but we were somewhat worried because of the Kurume nurseryman's belief that it would be difficult to find any of these Rhododendrons.
The last lap to the foot of Ichibusa was an after-dark crossing of Yuyama Pass, from Miyazaki into Kumamoto Prefecture. The Miyazaki side of this pass convinced us that the comfortable little Toyota sedan ranks above the legendary European cars which one reads about in the National Geographic . And the Kumamoto side was a lesson in skillful maintenance which could well be emulated in other prefectures and American states. Late bath and dinner at our inn were pure luxury and we arose early the next morning to drive up to the foot of the Ichibusa trail. Here, we were delighted to find that the rock was granite! Not yet having obtained the geological map, we didn't know what to expect, and this was highly encouraging. We rushed up through a beautiful cover of conifers, Azaleas, Magnolia, Skimmia, etc. Then, at 1400 m., the vegetation changed as suddenly as if we had gone to another continent; the beautiful ornamentals were replaced by bamboo, grass, dwarf alder, and some Pieris. Above this elevation we were off the granite and back onto the sandstone and shale of the Shimanto geological belt, and the vegetation continued bleak and monotonous all the way to the summit. On the far (i.e., the east) side of the summit ridge there were attractive plants of R. keiskei (No. 39) but no other evergreen Rhododendrons.
It was dark before we got back to the car, and we drove down to the inn much disappointed, considering a try on some other side of Ichibusa the next day. But, at dinner, our maid said we should drive a few kilometers west and north then climb to the ridge above Shiromizu-taki (Whitewater Falls).
The next morning, in gradually thickening rain, our companion on this trail was a farmer climbing back up to his home after a shopping trip. He recommended that we first try a ridge at about 800 m. elevation, but insisted that we should go from there to his home, up the small mountain valley. This first ridge ended at a ledge from which we could look down through the clouds and see our parked car, far below. Rhododendrons almost eluded us here, and we found only one plant (No. 40), but the character of this was sufficient to stimulate our interest. After pushing our way through a great deal of brush we returned to the valley and knocked at the door of the first farm house, but this was not the home of our trail companion. The lady who answered the door was courteous, but we got the impression that she was a little puzzled at people who didn't know enough to get in out of the rain, and we took a look at our current situation. Mrs. Doleshy's water-repellant clothing had reached a state of complete saturation but my waterproof parka was still doing some good, so she started down to the car with camera, etc., while 1 kept the maps and most of the food and headed toward a peak in the general direction of Ichibusa.
At the next farm I looked at the chrysanthemums in the flower garden and suddenly saw that they were growing around a huge and wonderful specimen of R. metternichii var. metternichii . The farmer, after carefully determining that I only wanted herbarium specimens and seed, pointed out the ridge where this plant came from, "not far at all", and wished me luck. Heading that way, I got on the wrong trail, came back to a third farm, and finally found our morning companion. He directed me to the right slope and, a few minutes later, appeared by my side in hard hat and raingear. At the top of the ridge (950 m.) there were fine plants of the Rhododendron, growing among sparse, wind-twisted conifers and generally about 2 m. tall. These were densely covered with foliage and tended to grow in the shape of a cone or pyramid. Over the ridge, on a steep, rocky north slope, they were competing quite successfully with larger conifers and grew as multi-stemmed plants to about 5 m. Ample seed was available on and behind the ridge, and this is our No. 41. Also, ignoring the waterfall from the sky, the same farmer insisted on picking and giving me all seed from a specimen which he had moved from the ridge to his flower garden. This No. 42 seed, I understand, was in great demand from the Seed Exchange, and several people have told us that they thought the farmer would select a winner from the wild population. He will be pleased to hear of this, if we visit him again, because his garden was very attractive.
He as well as as his neighbor tactfully made it clear that destructive collecting would have been discouraged, and I left with the comfortable feeling that this wild population was protected as effectively as any plants in Japanese or American national parks.
Several (days later, when we obtained a geological map of Kumamoto Prefecture, we could see that the Shiromizu-taki area was a N.W. extension of the granite which supported a rich flora on the lower part of Ichibusa but did not extend to the summit. Here as elsewhere, the preference of the Rhododendron for a particular type of rock seemed clear-cut; we had driven through many kilometers of the sedimentary rocks of central Kyūshū but found no Rhododendrons until we reached the granite of the Ichibusa area.
This was the fifth such observation on our 1967 trip. Rock preferences were equally clear at Jōkoji, Yokodake, Shakutake and Mt. Kuju. These preferences apparently are not related to chemical or mineral content, in most cases, because Rhododendrons seem equally at home on the dark lavas or on light-colored granite. Instead, the texture of the rock seems to be the important factor. Ponticum-group Rhododendrons are found on granular, porous or fine-cracked rock, and it seems likely that the reason is the ability of such rock to hold water and/or release water vapor from subsurface storage to the roots of the plant, where it may condense when the ground surface cools at night.
The Southern R. metternichii
Returning to our southern collections of
, it should be clearly understood that we did not "discover" this population. Our friends in Japan had been unable to tell us much about the locality, but the distribution maps showed that someone had found plants here.
We had imagined all kinds of things about these plants during the two years that had passed since we decided to visit the Ichibusa area. Perhaps, we thought, they would be transitional in the direction of var. yakushimanum . Also, we had corresponded with Tor Nitzelius, in Sweden, who had suggested that the various existing phases of R. metternichii might be the evolutionary product of two ancestors of past ages, one with 5-part and one with 7-part flowers, and that it might be possible to find remote populations which preserved these characteristics in almost pure form. Another very interesting suggestion was given us by Mr. Wada, who has noticed that the 7-lobed characteristic is highly dominant when crosses are made. He proposes that this characteristic may have originated as a sport and subsequently spread to the limits imposed by natural barriers. If this is the case, it might be possible to determine the approximate point of origin by locating the wild populations which are most purely separate.
We cannot be certain that the 7-lobed characteristic is particularly pronounced at this far-south locality, since we did not see the plants in flower. However, one of our regular procedures is to count the number of sections in all seed capsules collected, and we found an unusual degree of uniformity in those obtained from the wild plants here: 94% had 7 sections.
This leads to questions of correlation, i.e., is it possible to work backward and determine the number of lobes per flower by counting the sections per capsule? And, if there is variation in the number of capsule sections, is there likely to be variation in the number of flower lobes?
Usually it is assumed that a particular species or variety has flowers with a constant number of lobes and also has the same number of sections per capsule, although exceptions are noted in The Species of Rhododendron (Stevenson, ed., 1930). Also, Yamazaki, in the paper above cited, reports variability in the number of lobes per flower, and he suggests further study to determine whether there is corresponding variation in the seed capsules. In addition, Nitzelius, in his "Notes on Some Japanese Species of the Genus Rhododendron" ( Acta Horti Gotoburgensis , XXIVA, pp. 135-174), states that two of the capsules on the type specimen of R. metternichii are 8-chambered and he suggested that the number of flower parts is too variable to be of critical significance for identification of these species.
Our own comparisons of flowers with the corresponding capsules have, so far, been confined to R. makinoi and the American R. macrophyllum , and we have found some differences. Also, we have found that the flowers on cultivated plants of the Japanese Rhododendrons are not nearly so uniform as is commonly supposed.
In summary, we believe that the number of sections per seed capsule is, indeed, a general indication of the number of flower lobes. If all capsules have 5 sections we should expect all flowers to have 5 lobes. But, when there is variation in the number of sections per capsule, this may or may not indicate similar variation in the flowers. Actually, the variability of the capsules may only indicate a latent tendency toward flower variation, and the flowers may be more nearly uniform.
With these qualification in mind, one may turn to the capsule counts which are reduced to percentages and shown graphically in Fig. 38. These are from our 1965 and 1967 collections, and some idea of statistical reliability can be obtained from the number of capsules counted in each case (shown below the name of the plant).
Considerable variation is evident in most of these collections. In contrast, the uniformity of No. 41, the main wild population at Shiromizu-taki, is rather spectacular and may be close to the limit of uniformity to be expected in this group of Rhododendrons. No. 42, from a cultivated plant transplanted from the same population, had 25% 8-part capsules and appears to confuse the issue. However, these capsules were from a single plant, probably selected for extreme size of flower, and it seems unnecessary to attach much importance to the different count.
The uniformity of No. 41 suggests that this population could have been a source of the 7-part characteristic and has escaped or resisted any invasion of the 5-part characteristic. Therefore it is possible that these plants are the progeny of a sport or the survivors of a form which has become rare, but a definite opinion cannot be expressed without further knowledge of this species.
The vigor and adaptability of these plants in their present environment tends to dispel any impression that they are living fossils in precarious condition. The plants on the windy ridge top, growing to a height of about 2 m., were so dense that it was difficult to see through them. And those behind the ridge, competing with conifers, were producing good foliage and seed capsules at the unusual height of 5 m. In the farm gardens (perhaps with pruning) they were capable of growing as great cushions, up to 2.5 m. across by 1.5 m. tall, covered with capsules and buds. Here in full exposure there was some leaf scorching and insect damage, but hardly what one would expect from the summer drought-probably the worst in 60 years.
I could find no cases in which the plants held their leaves for more than 4 years, but this may also have reflected the unusual summer. Some of the seed capsules were the largest we have seen in Japan, 28 mm. long, possibly indicating a large flower. I did not obtain any satisfactory count of capsules per truss; these were very ripe and saturated with water, and they broke up when picked.
Considering now the matter of attractive appearance, it is clear from the capsule counts (Fig.38) that this population is not transitional toward R. metternichii var yakushimanum , and this is confirmed by the lack of any dense tomentum on stems and seed capsules. However, the open-minded grower will perhaps he receptive to the idea that there can be at least one or two good phases of R. metternichii besides var. yakushimanum .
As in the case of the other Kyūshū populations of R. metternichii var. metternichii , the leaves of this plant have some tendency toward the domed shape seen on var. yakushimanum , and the color is the same rich, deep bottle-green. Indumentum on leaf undersurfaces is thick and varies in color with aging as on Mt. Kuju specimens (i.e.. brightest on the previous year's leaves). Actually, the only significant difference I could see between this and the other Kyūshū plants was more a matter of impression than precise measurement: The leaves seemed to be held more horizontally and to overlap a little more. The result is a somewhat distinctive appearance which may or may not be preferred, but which I found appealing.
In view of capsule size and the nearly uniform lobe counts, it is possible that the most important differences will be in the flowers, and these should be very interesting, either in the wild or in cultivation.
This concluded our observations of R. metternichii in Kyūshū, and we drove on south to Ebino and revisited the slopes covered with R. kiusianum (No. 13) which we had seen two years earlier, then turned in the car at Miyazaki and flew over to Kōchi, on the south coast of Shikoku. We had intended to look at R. metternichii in the mountains of this island but, instead, rented another car and drove out to see the subtropical plants on the rocky coast of Cape Muroto, then returned to visit the botanic garden and museum built in memory of Dr. Tomitaro Makino, who died in 1957. Born in a small town near Kōchi, he became one of the world's foremost botanists and is much revered.
From the staff of the garden we learned of the surprising occurrences of R. brachycarpum on the two highest mountains of Shikoku, and also were told that R. metternichii var. metternichii is rather rare on this island, in comparison with var. hondoense . However we have since learned from Mr. Wada that most of the plants he has received from Shikoku appear to be var. metternichii . In view of these interesting puzzles, we are not at all sorry that the nicest inn we know about is located in Kōchi.
Upon return to Seattle we were welcomed by a Plant Quarantine officer, who explained us to the Customs officer and assured us that his colleague, Dr. Brown, had been receiving and caring for our shipments. Of this we had no doubt, but a cordial greeting after the long flight was very pleasant indeed.
As stated earlier in this Report, plants similar to
but with 5-lobed flowers were described by Yamazaki in 1964 as
(Journal of Japanese Botany, 39:1, pp. 13-18). However, K. Wada had earlier recognized the distinctness of these plants, and he has distributed them as
(a name of which he is the author) for at least 30 years. This name was included in his internationally-distributed 1938 catalog (and probably in his 1936 catalog). Moreover, in the 1930s, he sent seed of this plant to E. J. P. Magor, of Lamellen, St. Tudy, Cornwall, England, and Dietrich Hobbie obtained a part of this seed but labeled the plants as
by error. This incorrect spelling was followed in
The International Rhododendron Register
(Royal Horticultural Society, London, England, 1958), and was also included by Hobbie in a paper for the 1959
Rhododendron and Camellia Year Book
, of the Royal Horticultural Society. In this paper Hobbie praised the plant as a good parent for hybrids.
Under the rules for priority of name, the listing in the internationally-distributed 1938 catalog constituted effective publication, and it appears that the Wada name should be considered valid and legitimate. However, if we follow Ohwi in treating these populations as varietal forms of R. metternichii , the name becomes RHODODENDRON METTERNICHII VAR. METTERNIANUM (Wada).
As stated by Yamazaki when he described it as R. metternichii var. kyomauruense , the variety is distinguished as follows: A typo foliis subtus glabrescentibus, corrollis pentafidis differt. (Differs from the type in having leaves glabrescent below and corolla 5-lobed.)