rLORA OF THE SUNDRIBUNS. 
265 
suppose that the pendulum-like bird* migrations which alternate with 
the monsoons throughout the submeridional ranges of hills and islands 
of Eastern Asia, are chiefly responsible for the introduction of such 
species into the Sundribuns. The figures, though too meagre to be 
conclusive, are not contrary to this deduction, which is in keeping 
with observed facts as regards the Andamans. 
Passing now to the various inanimate agencies of dispersal, we 
have first to deal with species that are introduced by wind. Space 
forbids an examination in minute detail of the features of distribution 
of each of these plants, the requisite data for which are, however, 
given in the systematic census. It is sufficient here to say that they 
may be divided into four natural groups : {a) those with light spores 
(Vascular Cryptogams), of which the epiphytic forms either are cosmo* 
politan or are at least widely disseminated in the Old World and the 
terrestrial are at least widespread in South-Eastern Asia ; [b) those with 
seeds or fruits of some size provided with a feathery pappus, a coma, 
or some equivalent arrangement,^ — again either cosmopolitan or, at 
least, widespread in South-Eastern Asia; those with seeds 
provided with wings, of which we have but two examples, a Dolichan^ 
drone widely spread in South-Eastern Asia, and a Dioscorea that is 
found everywhere in the tropics of the Eastern Hemisphere ; lastly, {d) 
those with very small and light seeds (Orchids) apparently exceedingly 
well adapted for dispersal by winds but nevertheless with often a 
remarkably localised distribution. The general features of the distri- 
bution of the 50 species of the class are : — 
Distributed both westward and eastward 
Cosmopoh’tan in the Tropics .... 6 
Tropics of Eastern Hemisphere, Australia, Poly- 
nesia . I 
Tropics of Eastern Hemisphere, Australia . . 3 
Tropics of Eastern Hemisphere, Polynesia . . 3 
Tropics of Eastern Hemisphere . . . >3 
South-Eastern Asia, Northern Australia, Polynesia 1 
South-Eastern Asia, Northern Australia . . 2 
South-Eastern Asia, Melanesia . . . .1 
South-Eastern Asia . . . . • .11 
India, Eastern Himalaya, Indo-China , . *3 
India (Circars), Tenasserim , » . , i 
Distributed eastward only . . . . . , 
Indo-China, Malaya, Northern Australia . * i 
Indo-China, Malaya ...... i 
Eastern Himalaya (Sikkim) and Indo-China . 6 
Indo-China * . . . , , . 2 
35 
