JARS v54n3 - Those Exciting Rhododendron Epidermal Appendages

Those Exciting Rhododendron Epidermal Appendages
Part IV: Subgenus Rhododendron
Arthur P. Dome
Seattle, Washington

This issue presents some of the interesting types of scales that appear on the leaves of some more of the popular members of the Subgenus Rhododendron and their taxonomic classifications.

The Winter 2000 issue of the Journal American Rhododendron Society (Vol. 54, No. 1) illustrates and describes some of the different types of scales or combinations thereof found on the leaves of this subgenus. It also covers the functions of these appendages as well, as even with the new developments of DNA technology they are still very important in classifying these plants. This information also pertains to this Part IV article.

The photographs of the leaves in this Part IV, as were those in Part II, were taken from plants growing at the Rhododendron Species Botanical Garden. The magnification varies from x10 to x50.

Underside of mature new leaf of R. charitopes ssp. charitopes Underside of mature new leaf of R. campylogynum
R. charitopes ssp. charitopes, S.* Rhododendron, Ss. Glauca. Mature new leaf underside
glaucous covered with papillae also vesicular and entire type scales.
Photo by Arthur P. Dome		 R. campylogynum, S. Rhododendron, Ss. Campylogyna. Mature new leaf underside
glaucous with papillae and small vesicular type scales.
Photo by Arthur P. Dome
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Underside of mature new leaf of R. cinnabarinum ssp. cinnabarinum var. roylei Underside of mature new leaf of R. hirsutum
R. cinnabarinum ssp. cinnabarinum (var. roylei), S. Rhododendron,
Ss. Cinnabarina. Mature year-old leaf underside green with entire type scales.
Photo by Arthur P. Dome		 R. hirsutum, S. Rhododendron, Ss. Rhododendron.
Mature new leaf underside with entire type scales.
Photo by Arthur P. Dome
Underside of mature year old leaf of R. keysii Underside of mature new leaf of R. saluenense ssp. saluenense
R. keysii, S. Rhododendron, Ss. Cinnabarina. Mature year old leaf
underside pale green with entire type scales.
Photo by Arthur P. Dome		 R. saluenense ssp. saluenense, S. Rhododendron, Ss. Saluenensia.
Mature new leaf underside with overlapping crenulate scales.
Photo by Arthur P. Dome
Underside of mature new leaf of R. spinuliferum var. spinuliferum Underside of mature new leaf of R. trichocladum var. trichocladum
R. spinuliferum var. spinuliferum, S. Rhododendron, Ss. Scabrifolia. Mature new leaf
underside showing acicular and filiform hairs as well as entire type scales.
Photo by Arthur P. Dome		 R. trichocladum var. trichocladum, S. Rhododendron, Ss. Trichoclada.
Mature new leaf underside, light green with vesicular scales.
Photo by Arthur P. Dome

Acknowledgments
The author is indebted to Steve Hootman, Co-Director-Curator, Rhododendron Species Foundation, Federal Way, Washington, for proofreading the text of this article.

References
1. Chamberlain, David, and Roger Hyam, George Argent, Gillian Fairweather, Kerry S. Walter. 1996. The Genus Rhododendron, Its classification synonymy. Edinburgh: Royal Botanic Garden Edinburgh.
2. Cowan, John Macqueen. 1950. The Rhododendron Leaf. Edinburgh: Oliver and Boyd.
3. Davidian, H. H. 1982. The Rhododendron Species, Vol. I. Lepidotes.. Portland, OR: Timber Press.
4. Cullen, J. 1980. Notes from the RBGE, Vol. 39,. Edinburgh: Royal Botanic Garden Edinburgh.

* S = Section, Ss = Subsection, ssp = Subspecies, var. = Variety, syn.= synonym.

Arthur Dome, a member of the Seattle Chapter, passed away on June 14, 2000. This article concluded his series on epidermal appendages.

by Chase Dooley