162 TRANSACTIONS OF THE [Sess. lxxxi 



Rh. mengtszense differs from its fellows in respect of this 

 indumental character by bearing on its mature leaf -petiole 

 and stems setae and gland-setae as a dense persistent and 

 thick coating. It is quite strigillose. Traces of these setae 

 are to be found upon and about the midrib, both above and 

 below the leaf, particular]}^ towards its base, and very large 

 punctulations occur all over the veins, so that I have no 

 difficulty in correlating this exceptional setose condition as 

 a special development within the typical evolution. 



Rh. ceraceum and Rh. lukiangense appear more excep- 

 tional. The leaf-surfaces here show no conspicuous red 

 punctulation, though there are traces of it, but are covered 

 with a skin of wax so prominent as to give them a smooth 

 aspect on the under side as if varnished. The glossiness is 

 less on the upper side. The stem is also wax-covered, and 

 so is the petiole, and when the stem and petiole shrivel in 

 drying the wax stratum scales ott' the surface in a series of 

 flakes which are found coating the parts as a white crust. 

 There are no hairs or glands or their vestiges visible on 

 the blades, petioles, and stems of this species. Certain 

 marks on the leaf-margin suggest vestiges of glands or 

 hairs, but not certainly, and we do not know the bud con- 

 dition of the species. These indumental characters in 

 Rh. ceraceuvi and Rh. lukiangense are not fundamentally 

 different from those in the rest of the series. There is 

 only an excess of wax and reduction in other indumental 

 elements. Suspicion, however, of its position as one of 

 the series might be aroused. In all its other features it 

 seems to show its descent in common with those of the 

 Irroratum series. Whilst I think tl\at the feature of indu- 

 mentum has been too much overlooked by workers amongst 

 Rhododendrons, I do not subscribe to any overrating of 

 its value as a phyletic character. It has not apparently 

 always the same construction in forms belonging to the 

 same phylum, no more than it has in other genera. But 

 differential — and critically so — it is in some cases where the 

 a[)praisement of other characters has in the past proved 

 faulty for specific determination. I will say this, that two 

 plants in which the construction of the indumentum is 

 different are not the same species, and conversely, two 

 plants which have indumentum of the same construction 



