52 THE STORY OF THE PLANTS. 



thus withdraw their living material into the bark 

 in autumn ; but they attain much the same end in 

 different manners. Thus lilies and onions store 

 the surplus material they lay by during the sum- 

 mer at the base of their long leaves, and the 

 swollen bases thus formed produce what we call 

 a bulb, which carries on the life of the plant to 

 the next season. Other plants, like the common 

 English orchids, store material in underground 

 tubers; while others, again, and by far the great- 

 er number, so store it in the root, which is some- 

 times thick and swollen, or in an underground 

 stem or root-stock. In most cases, however, per- 

 ennial plants take care to keep over their live 

 material from one season to the other by some 

 such means of permanent storage. They are, so 

 to speak, capitalists. Natural selection has of 

 course preserved those plants w^hich thus laid by 

 for the future, and has killed out the mere spend- 

 thrifts which were satisfied to live for the fleeting 

 moment only. The soil of our meadows in win- 

 ter is full of tubers, bulbs, and root-stocks; while 

 our shrubs and trees carry over their capital from 

 season to season in their living bark, secure from 

 injury. In one way or another all our perennial 

 plants manage to tide their living green-stuff, or 

 at least its raw material, by hook or by crook, 

 over the dangers of winter. 



I have given so much space to the subject of 

 leaves because, as you must see, the leaf is really 

 the most important and essential part of the en- 

 tire plant — the part for whose sake all the rest 

 exists, and in which the main work of making 

 living material out of lifeless carbonic acid and 

 water is concentrated. 



