360 THE SELF-FERTILIZATION OF PLANTS. 



are fertile, is because they are fully and propor- 

 tionately developed; while, the reason the unenclosed 

 flowers are sterile, is because, in the feature of enclo- 

 sure, and most, probably, in other characters, they are 

 deficient. The smallness of the enclosed flowers, is a 

 feature which weighs but little, in the account of fer- 

 tility, in comparison with disproportionate develop- 

 ment. The mere lack of enclosure, would suffice to 

 make an appreciable difference in fertility only after 

 very long continued self-fertilization. But, this lack of 

 enclosure, is doubtless conjoined with other structural 

 defects. 



On p. 229, Animals and Plants, &c, Darwin says, as : 



"In several well authenticated instances, already 

 often alluded to; certain species have been affected, in 

 a veiy different manner, for they have become self-im- 

 potent, whilst still retaining the capacity of fertilizing, 

 and being fertilized, by distinct species." 



Frequently, individuals only, of a species, are modi- 

 fied in character, and have parts reduced to a rudimen- 

 tary condition. These individuals, of the species, will 

 of course be sterile; while those, individuals of the 

 species, which are unmodified, or very little modified, 

 will preserve their fertility. Of such cases, Darwin 

 really speaks, in the following remarks (page 168, 

 Animals and Plants, &c.) : 



"We now come to cases clearly analogous with 

 those just given, but different, inasmuch as individual 

 plants alone, of a species, are self-impotent. This self- 

 impotence does not depend on the pollen, or ovules, 

 being in a state unfit for fertilization, for both have 

 been found effective, in union with other plants of the 



