198 



Davis. 



when selfed. De Tries ('13, p. 181) reports that attempts to self-polli- 

 nate reciprocal crosses between the Dutch miirieata and gigns have proved 

 ineffective and my later experiments have so far failed in the attempt 

 to obtain seed from the Fi hybrids. In my last effort (1913) I adopted 

 a suggestion of Prof. DE Tries and grew reciprocal hybrids between the 

 Dutch muricafa and g/gas in a soil treated with bone meal about 1 kilo- 



Fig. 19. Rosette of hybrid, 12'12ga, gigas X muricaia "W, nearly mature, leaves 

 somewhat crinkled in older rosettes. Clearly a blend of parental characters. 



gram to each square meter, but, although the cultures were vigorous 

 and flowered very freely, I obtained no seed after numerous self-polli- 

 nations. .\lthough there is much evidence that this self-sterility of the 

 Fl hybrids between muricafa and gigas is due to physiological causes 

 rather than to peculiarities of gametic constitution it is not clear where 

 the difficulties lie. 



My second study also involved tiie race of muricata froui Woods 

 Hole. A cross 12'12 gigas X muricata W gave a very small yield of 



