THE FLOWER AND THE BEE 



even noticed the frequent occurrence of cross-pollination, and 

 remarks that "it seems that nature is unwilling that any 

 flower should be fertilized by its own pollen." He described 

 the manner in which some five hundred flowers are pollinated; 

 but as he knew little about insects he did not pay much atten- 

 tion to the different kinds of visitors. 



But while Sprengel had learned the secret of flowers and knew 

 that their colors, odors, and forms were not useless characters, 

 he failed to discover why cross-pollination is beneficial; and 

 this omission, as Mueller has remarked, was for several genera- 

 tions fatal to his work. In 1841 Robert Brown, an eccentric 

 English botanist of great learning, advised Darwin to read 

 Sprengel's book. "It may be doubted," says Francis Darwin, 

 "whether Robert Brown ever planted a more beautiful seed 

 than putting such a book into such hands." Thus is the torch 

 of learning, shining with ever-increasing effulgence, handed on 

 from one investigator to another. Darwin was already en- 

 gaged in studying British orchids, of which he wrote to Ben- 

 tham: "They are wonderful creatures, these orchids." His 

 interest in the structure and pollination of these curious plants 

 was greatly increased by reading what the old German pastor 

 had done. Darwin soon discovered that frequent crosses in- 

 crease both the vigor and productiveness of the stock, and 

 that an occasional cross is indispensable. The principal agents 

 which nature employs for this purpose are insects, birds, wind, 

 and water. So impressed was Darwin with the importance of 

 cross-fertilization that he closed his famous book on orchids, 

 which marks the next great epoch in flower ecology, with the 

 words: "Nature abhors perpetual self-fertilization." "The 

 charm," says Mueller, "was now broken, and the value of 

 Sprengel's work was at once recognized." "The merits of poor 

 old Sprengel," says Darwin in his autobiography, "so long 



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