E — 
42 BALFOUR—NEW SPECIES OF RHODODENDRON. 
series is as yet small—Rh. lacteum, Franch., Rh. Beesianum, Diels, 
Rh. Traillianum, Forrest et W. W. Sm., Rh. colletum, Balf. f. et 
Forrest, make a quartette at the moment. That there are others I 
know, but whilst a considerable number of specimens of members 
of the phylum are now in our possession, many are without flower 
—showing foliage alone or foliage with fruit. The specific segre- 
gation of this material in the circumstances is no easy task, and 
indeed must be in a measure tentative, awaiting confirmation 
by the collecting of future explorers. Meanwhile, for the informa- 
tion of anyone who wishes to know how to recognise a member 
of the Lacteum series—a truly natural phylum,—and as a basis 
for future work, let me say that the characters of the indumentum 
of the under side of the leaf are crucial. It is thin buff-coloured 
scintillating unistrate, forming a smooth soft surface consisting 
of rosette-hairs with some 4 to 5 broad short vesicular thin- 
walled unicellular branches arising from a common short base. 
The rosettes are quite separate though their branches more or 
less overlap, and it is the walls of these empty branch-cells which 
cause the iridescence of the leaf-surface when looked at through 
a magnifying glass. The rosettes are easily separated from the 
surface of the leaf. If they are scraped off on to the surface of 
a microscopic slide and a drop of alcohol be added to them, they 
diffuse through the fluid like a fine powder, and their form can 
then be readily seen. In no other Rhododendrons that have 
come under my observation is there an indumentum of this kind. 
It is to my present knowledge a critical differential character of 
_ Rh. lacteum and its allies, and it has the advantage of a character 
to be ascertained without difficulty. As I have described it, the 
character is not differential of species: But there are minor 
distinctions between the rosettes that are certainly specific in 
species recognisable by other characters. Its chief value lies in its 
differentiation of the Lacteum series. There are other Rhododen- 
drons which show a thin buff-coloured scintillating indumentum 
forming a more or less smooth surface, but on applying in these 
eases the test I have mentioned the indumentum elements will 
not diffuse like a powder in the fluid—they adhere in groups, and 
have to be torn apart,—and this because the construction of the 
hairs is different and their branches interweave and interlock, 
holding the hairs together. 
Rhododendron comisteum,* Balf. f. et Forrest.7 
Leafy shrub of slow growth barely 1 m. high annual incre- 
nmenhe small, the leaves and scale-leaves (both outer and inner) 
* xoulotedc, to be taken care of—as a most charming plant for the garden. 
| Rhododendron comisteum, Balf. f. et Forrest.—Frutex nanus dense foliatus 
foliis per annos persistentibus. Rami dense rufescenti-tomentosi, to 
