11-2 LIFE OF 



flowers cross-fertilised bear more and larger seeds, 

 which produce healthier offspring than those fertilised 

 from their own pollen ? This Darwin set himself ex- 

 haustively to do. For more than a dozen years after 

 his book on orchids appeared, unwearied experiments 

 on plants were progressing, and nature was being ques- 

 tioned acutely, untiringly. Competitive germination was 

 carried on. The two classes of seeds were placed on 

 damp sand in a warm room. As often as a pair germi- 

 nated at the same time, they were planted on opposite 

 sides of the same pot, with a partition between. Besides 

 these pairs of competitors, others were planted in beds, 

 so that the descendants of the crossed and self-ferti- 

 lised flowers might compete. The resulting seeds 

 were carefully compared, and their produce again com- 

 pared. Species were selected from widely distinct 

 families, inhabiting various countries. From a large 

 number of plants, when insects were quite excluded by 

 a thin net covering the plant, few or no seeds were pro- 

 duced. The extent of transport of pollen by insects was 

 unveiled, and the relation between the structure, odour, 

 and conspicuousness of flowers, the visits of insects, and 

 the advantages of cross-fertilisation was shown. "We 

 certainly," says Darwin, " owe the beauty and odour of 

 our flowers, and the storage of a large supply of honey, 

 to the existence of insects." The multitude of facts 

 gathered about insects could only have been discovered 

 and rightly appreciated by one who was a true entomolo- 

 gist as well as a botanist. 



In the last chapter of the book the author discusses 

 with remarkable power the causes of the phenomena he 



