384 



FOUNDATIONS OF BOTANY 



of zoology as well, that plants and animals do not make 

 unrewarded outlays for the benefit of other species. Evi- 

 dently the pulp of fruits is not to be consumed or used 



FIG. 273. Barbs and Hooks of Burs. 



I, barbed points from fruit of beggar 's-ticks, magnified eleven times ; 

 II, hook of cocklebur, magnified eleven times ; III, beggar's-ticks 

 fruit, natural size ; IV, cocklebur hook, natural size. 



as food by the plant itself or (in general) by its seeds. It 

 is worth while, therefore, for the student to ask himself 

 some such questions as these : 1 



(1) Why is the pulp of so many fruits eatable ? 



(2) Why are the seeds of many pulpy fruits bitter or 

 otherwise unpleasantly flavored, as in the orange ? 



(3) Why are the seeds or the layers surrounding the 



1 See Kerner and Oliver's Natural History of Plants, Vol. II, pp. 442-450. 



