BALFOUR—NEW SPECIES OF RHODODENDRON. 67 
divide. Lat. 28° 25’ N. Alt. 14,000 ft. Open rocky slopes 
and on the margins of pine forests. Shrub of 2-4 ft. Flowers 
rose. G. Forrest. No. 14,368. July 1917. 
S.E. Tibet. Tsarong. On Ka-gwr-pw, Mekong-Salween 
divide. Lat. 28° 30’ N. Alt. 12,000-13,000 ft. Open rocky 
slopes. Shrub of 4-6 ft. Flowers white, flushed rose exterior, 
without or with very few markings. G. Forrest. No. 14,732. 
Aug. 1917. 
S.E. Tibet. Tsarong. G. Forrest. Nos. 14,776, 14,786. 
Sept. 1917. Duplicate in fruit. 
S.E. Tibet. Tsarong. G. Forrest. No. 14,799. Duplicate 
in fruit. 
W.N.-W.-Yunnan. G. Forrest. Nos. 14,802, 14,806. Sept. 
1917. Duplicate in fruit. 
. Tibet. Tsarong. On Ka-gwr-pw, Mekong-Salween 
divide. Lat. 28° 30’ N. ‘Alt. 14,000 ft. On open rocky slopes. 
Shrub of 6-10 ft. In fruit. G. Forrest. No. 14,810. Sept. 
IgI7. 
The striking feature of this Rhododendron is its indumentum 
on the leaf under surface. In the bud both surfaces of the leaf 
are densely clad by hairs. Those on the upper surface are 
beautifully shaped flocks having a definite stalk; from its 
base upwards proceed long unicellular thick-walled pointed 
branches curling and more or less interlocking with those of 
neighbouring hairs. As the leaf unfolds these flocks fall off, 
a few withered vestiges remaining. The lower indumentum 
is composed of two kinds of hairs, some—fewer—like those 
of the upper surface, others with thin-walled septate vesicular 
branches which are agglutinate almost from the first, and 
between which the thick-walled floccose hairs pass upwards. 
When the leaf expands these agglutinate hairs form a thin 
pellicle bright yellow in colour, apparently from a secretion of 
wax, and the pellicle is continuous over the whole under surface. 
But long before the leaf has reached adult size a remarkable 
change takes place in two directions. First of all in colour. 
The hairs change to a red-brown, as if infiltrated with a 
resin-like substance. Then the indumentum pellicle breaks up 
as the leaf extends into patches equally distributed over the 
surface of the leaf. So uniform is the size of the patches, 
although their outline is not so, and so uniform their distribu- 
tion, that the phenomenon can hardly be accidental. The leaf- 
surface appears covered by reddish-brown scale-like patches 
separated by intervals in which the green leaf-tissue is visible 
thinly concealed by bases of hairs detached and held in the 
agglutinate scale-like patches. These scale-like patches seem 
to dry up and are separable from the leaf. In older _— they 
