THE SELF-FERTILIZATION OF PLANTS. 369 



in the conditions necessary to retain such variations ; 

 and if, in addition, the new soil is not capable of de- 

 veloping some other characters which the plant has 

 lacked, and which may serve to keep up the comple- 

 ment of developments, necessary to any degree of fer- 

 tility, the plant will manifestly become sterile. 



Darwin says, that, "Any two self-impotent plants 

 can reciprocally fertilize each other." This conclusion 

 of his is supported by an immense array of facts. But, 

 when the cause is known, the said conclusion is seen 

 to be a little too broad. Self-impotent plants can, and 

 generally do, fertilize each other. But, this is, be- 

 cause the plants are somewhat different in structure. 

 Where two self-impotent plants are similarly defective 

 in structure, they cannot fertilize each other. Plants 

 are self-impotent, because they are defective in struc- 

 ture, and because, in the self-impregnation, each re- 

 productive element supplies the forces, of exactly 

 the same number (and no more) of characters, which 

 the other element does. But, when two individual 

 plants, with any positive differences distinguishing 

 them, cross, the reproductive element of each has 

 some positive character or characters to contribute 

 to the formation of the seed, which the other plant 

 has not; and, between the two of them, they make up 

 the forces of the number of parts requisite for success- 

 ful fertilization. To Darwin, the fact of the capacity 

 of two self-impotent plants to fertilize each other, is 

 simply anomalous. 



He says (p. 174, Vol. ii, Animals and Plants, &c): 



" It is interesting (!) to observe the graduated series, 

 32 



