58 
RE POUT ON THE MOSSES 
collection dealt with here includes representatives of all three. Thus, 
Drude's regions 5 and 6 respectively, and the Himalayan region, are 
represented by the species, among others, in the following three groups 
(1) Vesicularia Montagnei, Mnium succulent um. 
(2) Barbella enervis , Leucobryum j accuse, Moribund aria jlori - 
bunda, Campylium glaucocarpum, Physcomitrium repandum. 
(8) NecJceropsis acutata, V csicularia succosa , lly pottery gium 
jlavo-limbatum, Tremaiodon conformis. 
All the species in (1) and (2) were collected, as would be expected, in 
the plains abound Kobo or at quite low altitudes in the hills. As soon as 
we ascend to the higher levels, the Lower Hill and Upper Hill Forests 
described by Mr. Burkill (The Botany of the Abor Expedition— Report 
of the British Association, Section K, Dundee, 1912), these floral relations 
cease and the affinity of the mosses with those of the Himalayan range 
becomes at once evident as in (3) . 
If is obvious that the geographical and climatal conditions that permit 
a given area to be the meeting place of several phyto-geographical regions, 
may also, provided the conditions persist over a sufficient period, permit 
also of that area being a centre of distribution back into the several 
regions concerned ; indeed identical facts of distribution might in certain 
cases be explicable on either ground. This should perhaps be taken into 
account in considering the plant distribution in this district. 1 have not 
attempted to ascertain what body of evidence there is for looking upon 
the Assam or Khasian region as a centre of dispersal, either from the 
bryophytes or other groups of plants, but the distribution of one genus 
of mosses, at least, is certainly highly suggestive in this direction. I 
refer to the genus Symgphyodon. This is a clearly characterized and 
striking genus, of which at present, so far as I am aware, eighteen 
species are known. Of these the Philippines, New Caledonia and S. 
China furnish one endemic species each, the remaining 15 being en- 
tirely confined to the Indian and Malayan peninsulas, except that 
one species, S. Perrottetii with a wide distribution in India extends 
also to Java and the Moluccas. Fourteen species, therefore, 
out of eighteen find their limits within the East Indian peninsular 
region, and of these eleven are confined to the area centring 
round Khasia, from Nepal and Bhutan on the west (including 
four undescribed species of Brotherus in Sikkim), and an unpublished 
species of Mitten's from Burma on the south-east ; five or six of 
them, including the two species described in this paper, occurring 
in, and four being coniined to this part of Assam. It seems 
impossible in such a case to look upon the Kha&ian district in any 
