200 THE STORY OF THE PLANTS. 



Other desert plants have often to resist immense 

 drought, and therefore possess extraordinary vital- 

 ity in this way. They will grow again from the 

 merest cut end under favourable conditions. 



These few short hints as to the life-history of 

 various plants in different circumstances will serve 

 to show you how vast is their variety. Every plant, 

 indeed, has endless ways and tricks of its own; 

 and every point in its structure, however unob- 

 trusive, has some purpose to serve in its domestic 

 economy. Thus the ivy-leaved toad-flax, which 

 grows on dry walls, has straight flower-stalks, 

 which become bent or curved when the flowering 

 is over. Why is this ? Well, the plant has ac- 

 quired the habit of bending round its flower-stalk 

 after the blossoming season, because it cannot 

 sow its seeds on the bare stone, so it hunts about 

 diligently for a crevice among the mortar into 

 which it proceeds to insert its capsule, so that 

 the seedlings may start fair in a fit and proper 

 place for their due germination. So, too. the 

 subterranean clover, growing on close-cropped 

 hillocks much nibbled over by sheep, where its 

 pods of rich seeds would be certainly devoured 

 if exposed on a long stalk like that of other 

 clovers, has developed a few abortive corkscrew- 

 like blossoms in the centre of its flower-head, by 

 whose aid the whole group of pods burrows its 

 way spirally into the soil beneath; so that the 

 plant thus at once escapes its herbivorous ene- 

 mies, and sows its own seed for itself automat- 

 ically. It would be impossible in our space to do 

 more than thus briefly indicate by two or three 

 examples the immense number and variety of 

 these special adaptations. Every plant has hun- 

 dreds of them. '1 here is not a tiny hair on the 



