180 Plant Life and Evolution 



humming-birds; while in South Africa, the scarlet 

 Aloes and coral trees (Erythrina) are particularly 

 favored by the sun-birds. 



Whatever other advantages may come from 

 cross-pollination, increased variability is undoubt- 

 edly one result, and this may account in part for the 

 rapid evolution of new forms among the angio- 

 sperms, and their enormous preponderance at the 

 present time. 



Fruits of Angiosperms. The fruits of the angio- 

 sperms show a variety, which while not equal to 

 that of the flowers, nevertheless is very great. The 

 lower types have the fruit in the form of a dry cap- 

 sule, which opens at maturity and scatters the seed, 

 or sometimes it may be an indehiscent one-seeded 

 fruit, like that of many grasses, or the buttercup. 

 Such fruits have often to depend upon chance for 

 their distribution of seeds, just as the lower floral 

 types are dependent upon the wind for transporting 

 their pollen. With the evolution of plants, however, 

 many modifications of the fruit arose as the result 

 of which the distribution of the seeds was facili- 

 tated. This distribution may be in some cases by 

 means of water, but more commonly it is due to the 

 wind, or the agency of animals. Of fruits adapted 

 to water transport, the cocoanut is the classic 

 example. The gigantic seed, enclosed in its thick 

 water-proof covering, is eminently fitted for long 

 immersion without suffering, and may be carried 

 great distances by the ocean currents. Contrivances 



