131 



"(9) Pears produced by self-fertilization are very uni- 

 form in shape. They differ with crosses not only in size and 

 shape, but also in some cases in time of maturity and in 

 flavor." 



"(11) Self-fecunded pears are deficient in seeds, usually 

 having only abortive seeds, while the crosses are well sup- 

 plied with sound seeds." 



These same facts may be extended to many other plants, 

 but space will not permit us to dwell on this at greater 

 length. 



Superiority of Grossed Plants. Behrenssays: "Cross- 

 fertilization produces the greatest number of seeds capable of 

 germinating, while self-fertilization tends to produce few or no 

 seeds capable of germinating. Self -fertilized ovaries, on the 

 whole, produce fewer seeds than cross-fertilized. The seeds 

 produced by self-fertilization are on the average smaller and 

 lighter than those produced by cross-fertilization. The plants 

 from self-fertilized are on the average smaller and weaker 

 than those from cross-fertilized." 



^ Hermann Mueller^* comes to essentially the same con- 

 clusion, and adds, "that the product of self-fertilized can 

 resist unfavorable conditions, such as sudden changes of 

 temperature, much better. The superiority of crossed plants 

 does not depend on the mere separation of the plants, but it 

 brings together the properties of two individuals which have 

 a slightly different constitution." Grayi^ says: "It is seen 

 to be a part of the general 'economy of nature,' a phrase 

 which has a real meaning. One good illustration of it is 

 furnished by the pollen of flowers. The seeming waste in a 



14 Die Wechselbeziebungen zwischen den blumen und den ihre kreuzung 

 vermittelden insekten. 



15 Darwiuiana, p. 375. 



