How Plants Perpetuate Their Kinds 295 



thing is confirmed in general by the experience of animal breeders 

 who know that the parents must be not too nearly related if the 

 offspring are to be of the best. Indeed, it is evident that if pollen 

 and ovule belong to the same flower or even the same plant, we 

 have a near approach to vegetative reproduction; while the full 

 value of fertilization can be realized only when the uniting sex 

 cells come from different individuals. In a word, cross fertiliza- 

 tion has much the same advantage over close fertilization that 

 fertilization has over asexual reproduction; and this advantage 

 has sufficed to enable the kinds which have developed it to 

 triumph over those which have not. If it seems to the reader that 

 in cases like these Nature goes to a trouble out of all proportion to 

 the advantage attained, I would remind him that life is a kind of 

 race in which only a few can be winners; and that no effort can 

 be too great to put forth when to live is the prize and to lose is 

 death. 



There is, furthermore, still another matter of the highest impor- 

 tance which must receive our attention in connection with ferti- 

 lization. Everybody has heard something about Mendel's Law, 

 though it is not, as yet, widely understood. Mendel was an Aus- 

 trian monk, who, in his monastery garden, a half century ago, 

 began experimenting systematically upon heredity, and thereby 

 discovered the most important facts we yet know about that fun- 

 damental subject. In order that the characters transmitted by 

 each parent might be distinguishable in their offspring, he selected 

 as parents not plants of the same variety, but of distinct varieties 

 differing markedly in some given features; and furthermore, in 

 order to avoid the complications caused by cross fertilization, he 

 chose kinds which fertilize themselves, as do a number of culti- 

 vated species. Accordingly, taking Peas, which fulfil these con- 

 ditions, he bred together a kind with green cotyledons and an- 

 other with yellow cotyledons. The resulting offspring were of 

 course hybrids, but their cotyledons were not, as one would 

 expect, greenish-yellow, or yellowish-green, but were all yellow 



