1916-17.] BOTANICAL SOCIETY OF EDINBURGH 159 



{Rh. anthosphaerum, Rh. irroratum) to tawny shades (Rh. 

 agastuin, Rh. araiophyllum, Rh. ceraceum, Rh. hylo- 

 threptum, Rh. lukiangense, Rh. mengtszense, Rh. tana- 

 stylum) to cinnamon {Rh. adenosteononum). Apparently 

 several shades may be exhibited by one species according 

 to age. Three species stand out from their fellows by the 

 particularly glossy character of the leaf-surface due to a 

 wax coating. RJi. gyinnantlium has the upper surface as 

 if polished — a useful character for discriminating it at 

 sight from Rh. mengtszense in which the form of foliage 

 though larger is somewhat similar, — and Rh. ceraceum 

 and RJi. lukiangense have the under surface as if varnished. 

 Rh. araiophyllum, Rh. mengtszense, Rh. spanotrichuTn, 

 and Rh. tanastylum have also the under surface somewhat 

 glossy. Wax is, I believe, an epidermal formation in all 

 species of the section, only making itself conspicuous by 

 giving a glossy aspect in these cases I am naming here. 

 For a study of its development growing plants are required. 

 The poisoning of herbarium specimens with alcoholic solu- 

 tions must alter the appearances. As it appears the wax 

 is an infiltration of the outer cuticle out of which it can 

 be dissolved by benzole or other suitable solvent. This 

 is a different relation from that in species where the leaf 

 surface has a white or grey bloom, e.g. in Rh. formosum 

 or in the Lapponicum series. There epidermal papillae are 

 developed standing out from the leaf surface, and upon the 

 outside of these white wax granules cluster. There is no 

 varnishing of the surface as there is here in the Irroratum 

 series. One surface (the under) or both surfaces are to 

 correct observation conspicuously although minutely 

 punctulate in all species save perhaps in Rh. ceraceum, 

 and Rh. lukiangense. Apparently Rh. araiophyllum has 

 no punctulations on the under surface apai't from the 

 midrib and veins. Minute red or orange spots are dis- 

 tributed on midrib, primary veins, and the general reticula- 

 tion of the surface, and these may be seen also on the 

 cartilaginous margin. For an understanding of this 

 feature we must go to the buds and the young leaves 

 as they expand. The ptyxis of the leaves is revolute, the 

 young leaves standing in a cluster in the middle of the 

 bud-chamber after the fashion in all the large-leaved 



