1920] Collins: Inbreeding and Crossbreeding in Crepis Capillaris 211 



The results of inbreeding in Crepis support the statement of East 

 and Jones^ that in naturally cross-fertilized organisms the immediate 

 results of inbreeding are most emphatically injurious, but it must be 

 considered as an exception to their statement that "wild types, in 

 general, might not present such an appearance of injury under in- 

 breeding as shown by cultivated species." Maize is characterized by 

 the occurrence of both cross and self-fertilization, and when this 

 condition exists in wild species we may expect such species to behave 

 like maize when subjected to forced inbreeding. 



SUMMARY 



Inbreeding in a naturally cross-fertilized wild plant, Crepis capil- 

 laris, causes conditions in many ways similar to the conditions produced 

 by inbreeding in maize. 



The maximum reduction appears to be reached in the third and 

 fourth generations. 



Crossing inbred strains with non-inbred strains produces vigorous, 

 rapidly growing F^ plants. 



Inbred plants, when compared with crossbred plants, show a slower 

 rate of development during the entire period of growth. 



Some of the inbred strains showed pollen sterility by a reduction 

 in the number of mature pollen grains formed. 



Increased size of pots and quantity of soil did not affect the 

 relationship of vigor and of growth. 



The results of the experiments on Crepis indicate that the results 

 of inbreeding maize as reported by East and Jones* and others are 

 in no way peculiar to that species, but may be found to hold for other 

 species, either domesticated or wild, when similar conditions affecting 

 sexual reproduction obtain. 



3 Op. Cit. 



4 Op. cit. 



