14 THE DISPERSAL OF PLANTS [pt. i 



mechanisms, especially by help of birds; but also that (3) a large 

 number of species, even if few plants, travel by aid of "irregu- 

 lar" or accidental methods. If one could follow up the entire 

 history of distribution of plants about the globe, one would be 

 quite likely to find that all species sometimes travel in this way, 

 even though only very rarely. One would hardly expect to find 

 the buttercup, Ranunculus bulbosus, or Lathyrus pratensis, in the 

 willow-tops, yet both occur, though one docs not find such com- 

 mon plants as clover or daisy (44, p. 277). 



Two other important results also appeared: (4) that in only 

 two instances did a plant occur of which there was not a repre- 

 sentative actually growing on the soil within 200 yards. Even 

 in these cases it was quite possible that at the time of reaching 

 the willows the distance to be traversed did not exceed that 

 figure, for one of the two, Lactuca muralis, was recorded for the 

 same tree in Babington's Flora of thirty-five years earlier. In 

 any case, it was clear that as a rule transport was only over 

 short distances; and (5), a result which appeared on comparison 

 with similar work done elsewhere in Europe, that the proportions 

 of species distributed by the various mechanisms were much the 

 same (10, p. 120), so that one might be able to predict to some 

 extent the probable composition of such a flora. 



Another type of distribution was studied in working out, with 

 Prof. J. Stanley Gardiner, the flora of the Maldive Islands (138), 

 a group of coral atolls about 400 miles south-west of Ceylon, far 

 removed from other land. There is no reason to suppose that 

 any of their flora survives from the far-distant period when there 

 was probably a land bridge from India to Africa, so that they 

 probably formed a A'irgin area for the arrival of species from 

 elsewhere. Of their IGO species, 66 proved to be suited to carriage 

 by sea currents, possessing easily floated seeds or fruits, im- 

 pervious to salt water; 17 were bird-carried, with fleshy fruit, 

 4 were wind-carried, and there remained 73, probably mostly 

 due to unintentional carriage by man, but some doubtless 

 brought upon floating logs or in other ways. Again a large per- 

 centage of the species had thus arrived "irregularly." 



Another piece of work of this kind was done upon the flora of 

 Ritigala (117), a solitary precipitous peak, rising to 2506 feet in 

 the low-lying "dry" north country of Ceylon, about 40 miles 

 from the main mountain mass to the south, which forms part 

 of the "wet" zone. The dry zone receives practically no rain 

 during the six months of the south-west monsoon, and has thus 



