No. 31.— 1885.] CEYLON FLOEA. 



147 



were formerly in connection, or more often that each of them 

 has been in connection with some common point of origin 

 in the past. Thus, the floras of continental islands have, 

 as a basis, the plants of the mainland. All but the whole 

 of the English species are also European (the two excep- 

 tions being American), and it is reasonable to suppose that 

 their passage was effected at a time or times when the land 

 was in part continuous. The English Channel is nowhere 

 over 100 fathoms deep, and in most places not half that 

 depth. So too in Ceylon ; after deducting the endemic ones, 

 we have left about 1,929 species, all of which except about 

 130* are also found in the adjacent Peninsula of India. 

 No doubt the separation of the northern portion of Ceylon 

 from the opposite mainland is geologically recent, and the 

 species crossed over hither before it occurred. 



When, however, the localities in which a particular species 

 or group is found are widely separated (i.e., its area is discon- 

 tinuous) we have to assume often great changes of level, 

 producing, in present continental areas, various and different 

 arrangements of sea and land at different periods, and also 

 extreme changes of climate. For the operation of these is 

 required also a vast extent of time, but the revelations of 

 pulseontology and physical geology fully warrant the botan- 

 ist as well as geologist in forming such speculations. 



It frequently happens that the floras of two districts show 

 their affinity not by identity of species, but, less intimately, 

 by community of genera only, the species being different. 

 A good example is found in comparing our mountain 

 district with that of Southern India, say in both cases the 

 flora of the hills above 5,000 feet. A large, varied, and 

 beautiful vegetation characterizes both these regions, and 

 they are evidently very similar. Less than 400 miles 

 separates the summits of PidurutalagalaandDodabetta (and 

 there are half-way houses in the Pulnis and Anamalais). 

 Yet the curious fact presents itself that more than half the 

 species of our hills are not found in the Nilgiris or other hills 

 of the Indian Peninsula, but are endemic here, and probably 

 an even larger proportion of Nilgiri species do not extend 

 to us. The number common to both ranges is only about 



* This estimate is an approximation only. 



