SEED DISPERSAL BY ANIMALS 



CHAPTER XXX 



SEED DISPERSAL BY ANIMALS 



WE have seen how fleshy fruits may be dispersed or 

 scattered abroad by animals, but they do not as a rule eat 

 dry fruits unless it is for the sake of the seeds, in which case, 

 of course, the seed is crushed and digested, and ceases to 

 exist. But most dry fruits, achenes or even dry fruits dehis- 

 cent only after a considerable interval of time, have appen- 

 dages of various kinds which catch hold of animals and are 

 transported by them. 



I. Take a fruit of the Common Clotbur (Xanthium) and 

 notice : 



1. Its shape, size, color, and consistency. 



2. The two strong spines or hooks at the top. 



3. The smaller hooks thickly placed upon the sides. 



4. Make a sketch of this "fruit," or more properly bur. 



5. The involucre (enclosing two achenes) is modified to 



form the bur. A similar case is the Common 

 Burdock. 



II. Examine an achene of the Beggar-ticks (Bidens) 

 and notice : 



1. The body of the achene, its shape, etc. 



2. The terminal bristles (varying in number in different 



species) provided with 



