HOW PLANTS EAT. 55 



btcds. These buds are the foliage of the coming 

 season. The outer part consists of several 

 layers of dry brown scales, which serve as an 

 overcoat to protect the tender young leaves 

 within from the chilly weather. But the inner 

 layers consist of the delicate young leaves them- 

 selves, which are destined to sprout and grow 

 as soon as spring comes round again. Even 

 the scales, indeed, are very small leaves, with 

 no living material in them ; they are sacrificed 

 by the plant, as it were, in order to keep the 

 truer leaves within snug and warm for the 

 winter. Nor do the autumn leaves fall off by 

 pure accident ; some time before they drop the 

 tree arranges for their fall by making a special 

 row of empty cells where the leaf- stalk joins the 

 stem or branch ; and when frost comes on, the 

 leaf separates quietly and naturally at that point, 

 as soon as the valuable starchy and living 

 material has been withdrawn and stored in the 

 permanent layers of the bark for future service. 



Smaller and more succulent plants do not 

 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 summer at the base of their long 

 leaves, and the swollen bases thus formed pro- 

 duce what we call a bulbj 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 greater number, so store 

 it in the root, which is sometimes thick and 



