64 THE PLANT: A GENERAL EXTERNAL VIEW 



dandelion (see Figure ig), or of the stick tights you bring 



home on your clothes from an autumn ramble. (See Fig- 

 ures i6 and 17.) Think of the burs in a cow's 

 switching tail, or of the seeds in a bird's crop 

 which pass uninjured from 

 its body. (See Figure 18) 

 Think of buoyant fruits that 

 float over leagues of ocean 

 uninjured, or of the mud 

 carried on the feet of wading 

 birds; mud of the kind 

 from which Darwin got five 

 hundred and thirty-seven 

 seedlings out of three table- 

 spoonfuls. Thus we see 

 some reasons why buoyancy, 

 edibility, and the chnging 



power of fruits are of advantage to the kinds of plants 



which produce them. 



Fig. 18.— Fruit 

 of the mul- 

 berry. The 

 seeds of such 

 fruits pass 

 unin j ured 

 through the 

 alimentary 

 tract of 

 birds. 



Fig. 19. — The plumed 

 fruits of dandelion. 



21. Seeds. — Sometimes the seed itself bears the device 

 which secures a journey before germination. You may 

 recall the beautiful plumes of the milkweed seed by whiclf 

 it floats gracefully away when the pod bursts in autumn, 

 or in early spring. (See Figure 20.) It is from the soft and 

 abundant fibers that grow from the seeds of cotton that the 

 cotton of commerce is spun. 



But the main business of the seed is not dissemination. 

 That is only an important aid. The main business of the 

 seed is to protect and nourish that structure within it 

 which develops into the new plant. That structure, as 

 you have learned, is called the embryo. The embryo 



