No. 629] 



DARWIN AND HYBRIDIZATION 



543 



Darwin asserts that there is not a single case in his ex- 

 periments, 



Which affords decisive evidence against the rule, that a cross between 

 plants, the progenitors of which have been subjected to somewhat 

 diversified conditions, is beneficial to the offspring {ibid., 281). 



The fact that increased vegetative vigor in first gen- 

 eration hybrids was also sometimes accompanied by di- 

 minished fertility was likewise observed by Darwin, 



which are so far from being sterile, that their fertility is often actually 

 augmented, have, as previously shown, their size, hardiness and con- 

 tingencies of increased and diminished fertility (Ic, 2: 108). 



In the case of Darwin's experiments to determine the 

 relative effects upon vigor of selfing and crossing, respec- 

 tively, the data were determined chiefly with respect to 

 height and weight of the plants, which were grown on 

 opposite sides of the same pot in all instances. 



Eegarding the relative heights and weights of 292 

 plants, derived from a cross with a fresh stock, and of 

 305 plants either selfed or intercrossed, between plants 

 of the same stock and belonging to thirteen species and 

 twelve genera, Darwin says: 



profit immensely, though in different ways, by a cross with a fresh 

 stock, or with a distinct sub-variety. He emphasizes further. It can 

 not be maintained that the benefit thus derived is due merely to the 

 plants of the fresh stock being perfectly healthy, whilst those which 



Experiments were also made with plants belonging to 

 five genera in fonr different families. One of the most 

 interesting cases was that of a })lant of marjoram {Ori- 

 ganum vulgare). The height of the crossed was to that of 

 the selfed plants as 100:86. 



