246 L£SSONS WITS PLANTS 



XL VI. THE CROSSING OF PLANTS 



282. If the means for insuring cross -fertiliza- 

 tion are so general, it must follow that the cross- 

 ing of plants serves the plant some useful end. 

 It is known, as the result of much experiment, 

 that crossing results in strengthening or invigorat- 

 ing the offspring which grow from the seeds of 

 the cross-fertilized flowers. 



282o. The best results are usually obtained when the cross is 

 made between two distinct plants of the same kind, — not, on the 

 one hand, when made between flowers upon the same plant, nor, 

 upon the other, when made between wholly different kinds of plants. 

 The fullest information upon this subject will be found in Darwin's 

 "Effects of Cross- and Self -Fertilization in the Vegetable Kingdom." 



283. If marked benefits follow normal cross- 

 fertilization in wild plants, similar results should 

 follow in cultivated plants; and thare would seem, 

 therefore, to be reason to perform the pollination 

 by artificial means. 



283a. As a matter of fact, crossing is rarely done by man for 

 the purpose of improving the variety or kind, but rather — by cross- 

 ing plants of different kinds — to produce new varieties or kinds. 

 To this latter subject we shall revert at another time (534). 



284. Plants naturally cross under cultivation as 

 well as when growing in the wild, however, so thai 



