174 EFFECT OF CLIMATE ON PLANTS. 



The plants peculiar to the polar regions are ge- 

 nerally low, with small compressed leaves, and 

 flowers which are large in proportion to the other 

 parts ; those of New Holland are distinguished try 

 'Small and dry leaves, which often have a shrivelled 

 appearance. In Arabia, the plants in general are 

 low and dwarfish ; in the islands of the Mediterra- 

 nean and Archipelago, they are generally shrubby, 

 and furnished with prickles; while, in the Canary 

 Islands, many which in other countries are merely 

 herbs, assume the appearance of shrubs and trees. 

 Nature, however, has endowed some tribes with 

 the capacity of growing in almost all climates; 

 and this is fortunately the case with the grasses, 

 and with many eatable roots, such as carrots, tur- 

 nips, potatoes, so that these have followed man 

 into all the climates and quarters of the globe. 

 Between the tropics, where the heat is always high, 

 it often happens, that plants flower more than once 

 in the year. 



Light also, as well as heat, has a great effect 

 upon the colour and growth of plants ; so that, 

 when they are deprived of it, they become white 

 and colourless, and shoot up into pale weak stalks. 

 The outer leaves of a cabbage are green, but the 

 heart or inner part is nearly white, merely from 

 being shut up. Potatoes often grow in cellars, 

 where there is but little light and air ; and the 

 stems shoot to a great length towards the light, 



