14 



BOTANICAL GAZETTE 



[JANUARY 



0. LamarckianaXO. rubrinervis. — According to the deduc- 

 tions just given the expectation for this cross is 



O. Lamarckianay.0. rubrinervis = 

 (typica+velutina) X (deserens+velutina) = 

 typ.Xdes.+vel.Xdes.+tjrp.Xvel.+vel.Xvel. = 

 lucida subrobusta Lamarckiana empty grains 

 or 

 rubrinervis 



In the first place, I determined the amount of empty grains, 

 using the same method as in previous cases. 



The presence of empty grains is thereby proven, although the 

 percentages of germs are much smaller than would be expected; but 

 this may be due to quite different causes, as has been shown else- 

 where. 



In the second place, I studied the living progeny for the fourth 

 cross of this table and for a cross made in 1907 with another strain 

 of O. Lamarckiana. Each of these cultures was trimorphous, con- 

 taining the types Lamarckiana and lucida, and besides these either 

 subrobusta or rubrinervis (that is, tough or brittle). 



The expectation would be for equal parts, but for some unknown 

 reason the lucida almost always fall short of this. Apart from this 

 difficulty the results of these cultures coincide with the theoretical 



