144 BALFOUR—NEW SPECIES OF RHODODENDRON. 
W.N.-W.-Yunnan. Mekong-Salween divide. Lat. 28° 10’ N. 
Alt. 11,000 ft. Open rhododendron forest. Shrub of 6-10 ft. 
Flowers flushed pale rose with crimson markings. G. Forrest. 
No. 14,105. July 1917. 
S.E. Tibet. Tsarong. On Ka-gwr-pw, Mekong-Salween 
divide. Lat. 28° 35’ N. Alt. 13,000 ft. In open thickets and 
cane brakes. Shrub of 4-5 ft. Foliage only. G. Forrest. 
No. 14,939. Sept. 1917. 
W.N.-W.-Yunnan. Mekong-Salween divide. Lat. 27° 40’ N. 
Alt. 13,000 ft. In rhododendron forest. Shrub of 6-10 ft. 
Foliage only. G. Forrest. No. 14,959. Sept. 1917. 
On the Mekong-Salween divide this species represents Rh. 
phaeochrysum, Balf.f. et W. W. Sm. of the more eastern region 
of the Yangtze and the Chungtien Plateau in E.N.-W.-Yunnan. 
Rh. syncollum is easily diagnosed from its ally by its smaller 
leaves red-cinnamon-brown below, the more agglutinate and more 
shiny appearance of the under-leaf indumentum, by the shorter 
foliage-buds and the rounded not ovate outer scale-leaves and 
the smaller number of the inner scale-leaves, by the young leaves 
densely glandular above and below, the glandular pedicels and° 
calyx. The two species show an interesting contrast in the way 
the young leaves of the foliage-bud are protected. Rh. phaeo- 
chrysum has the young leaves characteristically revolute in bud 
and they have a small number of floccose hairs over both surfaces. 
Enveloping them are the inner scale-leaves of the bud several 
in number each of the innermost ones forming a hood of its 
upper half or third and so investing the young leaves at the 
danger point of their tip, the lower part of the scale-leaf being 
narrow almost petiole-like and occupying therefore less space 
within the basal part of the leaf-bud where the outer thick 
scale-leaves give an adequate protection. In Rh. syncollwm the 
revolute leaves have each of them a dense glandular covering 
both above and below, the glands being mixed with floccose 
hairs. Having this protection a smaller number of the inner 
scale-leaves suffices as an outside covering and these do not 
form so hooded an investment around the leaf-tips. In this case 
the protection rests mainly on gland-secretion, in Rh. phaeo- 
chrysum upon layers of leaf-scales. An interesting chapter 
might be written of such contrasts in other species of Rhodo- 
dendron—and indeed in species of other genera also—as they 
occur in the mountainous region of N.W. Yunnan and adjacent 
Burma and Tibet for the edaphic and epedaphic conditions are 
varied and change rapidly within a limited area stamping their 
impress upon the vegetation in the development within phyla of 
forms which diverge often only slightly yet sufficiently to claim 
specific rank. 
