26 PLOEA INDICA. 



fects of local circumstances and temporary associations, which 

 give a foreign colouring to everything surrounding them. 



The following remarks on the relation between climate and 

 the development of species in India, though crude, may prove 

 suggestive to those enabled to pursue this subject. Although 

 India presents greater contrasts of climate than any other area 

 of equal size in the world, we do not find that those genera and 

 species, which prevail over all its parts, are so variable in any 

 respect as are the plants of some countries which enjoy a more 

 uniform climate ; as an example, we may say that the species 

 forming the flora of New Zealand are, as a whole (proportion- 

 ately to the extent of the flora), far more variable than those 

 of the mountains or plains of India. Could this fact be ex- 

 panded, and, being confirmed in a wider survey, be proved to be 

 of general application, it wovld be one of the most important 

 data to start fi-om ru the investigation of those laws that regu- 

 late the development of varieties ; but we are not prepared to 

 say that a comparison of the species which inhabit the exces- 

 sive climates of difierent parts of India with those that inhabit 

 the uniform climates, supports this view : for instance, the 

 central or temperate regions of the Himalaya, where perennial 

 humidity and coolness prevail, are not peopled by very variable 

 genera and species, whilst the alpine regions that are charac- 

 terized by an excessive climate are so, and the annuals of the 

 hot plains are peculiarly sportive in stature, habit, hairiness, 

 foliage, and number and form of their smaller organs. 



Another point, intimately connected with- the question of 

 the power of climate in producing change in species, is the 

 relation that exists between the climate of an area, and the 

 number of species that inhabit it; and this afibrds a fertile 

 and most interesting field of inquiry in India, where so many 

 climates may be met with in a comparatively limited area. A 

 few facts have appeared to us worthy of notice, though as yet 

 far from well established : as that the equable climate met with 

 on the cool parts of the Khasia mountains and temperate re- 

 gions of the Himalaya, and on the hot humid coasts of Bengal 



