SUMMER MEETING. 39 



Knight. After experimenting in self-fertilization and cross-fertilization 

 in the pea and other plants, Knight, in 1799, laid down the law that in 

 no plant does self-fertilization continue for an unlimited number of 

 generations. This theory attracted very little attention until nearly 

 fifty years ago when Darwin came forward with his exhaustive experi- 

 ments and studies, from which he interpreted the natural law that "no 

 organic being fertilizes itself for a perpetuity of generations, but a 

 cross with another individual is occasionally — perhaps at very long in- 

 tervals — indispensable.'' Darwin showed that in all the higher forms 

 of animals the dexes are separate, in order that two different sources 

 of blood, or relationship, may be combined in the off-spring. He also 

 showed what we now so generally admit, that in-breeding diminishes 

 strength and productiveness, while a cross with a different strain in- 

 creases both. 



In his extensive work ''Cross and Self-fertilization in the Vege- 

 table Kingdom," Darwin conclusively proves the value of cross-fertili- 

 zation in plants. Giving years of patient, untiring labor to the work^ 

 he carried on a series of experiments in both self and cross-fertiliza- 

 tion in morning glories, petunias and other plants for a number of gen- 

 erations. He found that where continued self-fertilization was prac- 

 ticed, the plants diminished in size, vigor and productiveness with each 

 generation, and that a single cross of these seedlings with another 

 strain greatly improved them. He also cross-fertilized a great many 

 flowers, saving the seed and again crossing the seedlings grown from 

 them. These experiments were carried through many generations 

 with different kinds of plants. He found that cross-fertilized flowers 

 produced much larger, heavier and more vigorous seeds, and that the 

 seedlings grown from them were correspondingly stronger and more 

 fruitful. The most important conclusion resulting from Darwin's ex- 

 tensive studies along the line, during which he carefully compared his 

 own observations with those of other investigators, is expressed in 

 one of his own sentences — "Nature thus tells us in the most emphatic 

 manner that she abhors perpetual self-fertilizition." 



Experiments are ample to prove to us that cross-fertilization be- 

 tween plants of the same species is beneficial. Through laws of adap- 

 tation and selection the stronger, cross-fertilized plants would naturally 

 enough crowd out and supplant the weaker self-fertilized ones. It is 

 not surprising, then, to find that most of our flowering plants are actu- 

 ally constructed to bring about this result. Nature having so modified 

 their flowers as to render self-fertilization the exception rather than 

 the rule. In many flowers the pollen and the pistils are not ready for 

 fertilization at the same time, hence such flowers are dependent upon 



