TROPICAL FLORiVS 87 



such general fact to be explained. There may often, no doubt, 

 be more plants on some mountains than on the adjacent plains, 

 especially on open plains where social plants abound. On 

 mountains the botanist can often collect more species in the 

 same time, because diversities of soil and station are more 

 crowded together, but the accurate determination of the species 

 on areas from one square mile up to some hundreds of miles 

 shows that the fact is almost uniformly the other way. 



It is also of special interest to note that the well-known 

 fact in our own country, that a parish of 2 or 3 square miles 

 in area often contains more than half the flora of the whole 

 county many hundred times as great (as in the cases of Cad- 

 ney, Edmondsham, and Thames Ditton, given in the table), 

 appears to be even exaggerated in the more luxuriant tropical 

 forests, where a single square mile often contains as many 

 species as 100 miles in similar forests elsewhere. 



It is, however, interesting to note that when we compare 

 very small areas, measured by feet or yards instead of by 

 square miles, it is the temperate floras which seem to have 

 a decided advantage. Darwin records that on a piece of turf 

 3 feet X 4 feet long exposed to uniform conditions, (prob- 

 ably on the chalk downs of Kent or the Isle of Wight) he 

 found twentj" species of plants belonging to eighteen genera 

 (Origin of Species, 6th ed. p. 88). Sir Joseph Hooker in 

 the Himalayas, 11,480 feet above the sea, in the upper Lachen 

 valley, found a much richer vegetation. He says : ^^ Herba- 

 ceous plants are much more numerous here than in any other 

 part of Sikhim; and sitting at my tent door I could, without 

 rising from the ground, gather forty-three plants, of which 

 all but two belonged to English genera." And in a note ho 

 adds : " In England thirty is on the average the equivalent 

 number of plants which in favourable localities I have 

 gathered in an equal area." ^ 



In my limited reading I have found no other reference to 

 this form of species-abundance, nor do any of my botanical 

 I Himalayan Journals (olieap ed.), p. 335, 



