148 Plant Life and Evolution 



mersed in lakes or rivers. Like the fungi, many 

 angiosperms are parasites or saprophytes in their 

 habits, and like the fungi these may be quite desti- 

 tute of chlorophyll, and must, therefore, depend 

 upon other organisms for their supply of organic 

 food. 



Adaptability of Angiosperms. Perhaps in no 

 way is the adaptability of the angiosperms better 

 shown than in their relation to the animal world. 

 Serving as plants do for the food of a vast number 

 of animal forms, there have been evolved, in the 

 course of the development of both the animal and 

 plant kingdoms, numberless cases of special adapta- 

 tions of which the plants have taken advantage. 

 This is seen perhaps most perfectly in the evolution 

 of flowers, whose peculiarities are very generally 

 associated with cross pollination through the agency 

 of insects or birds. The peculiar modifications of 

 the latter, for instance, the mouth parts of bees or 

 butterflies, or the beak of the humming birds or 

 honey suckers, are clearly correlated with floral 

 structures. Many types of fruits also are associated 

 with modifications in animal structures. The teeth 

 of many mammals, and the beaks of certain birds, 

 are undoubtedly adaptations for feeding upon cer- 

 tain types of fruits, and the importance of animals, 

 especially birds, in the distribution of the seeds of 

 many plants is sufficiently well known. 



Although it is almost certain that all of the angio- 

 sperms have arisen from a common stock, the range 



