Breeding experiments which show that hybridisation and mutation etc. 267 



with, the lata foUage and the semi-decumbent habit ; and this may 

 be combined with various other characters derived by inheritance 

 from either parent. In the case of the lata ruhricalyx plant, one of the 

 germ ceUs from which it originated contained 8 chromosomes, and 

 one or both bore the character R. I laave shown (Gates, igo8) that 

 pollen grains containing 8 chromosomes are actually produced occa- 



Fig. 25. Scmilata mutant from grandifiora X riibricalyx, Fj. 



sionally in Oenothera. Doubtless the same process also occurs occa- 

 sionally in the megaspores. 



It is, therefore, obvious that the process by which 0. lata ori- 

 ginates from any Oenothera having 14 chromosomes, is entirely distinct 

 and independent of the regular redistribution of characters after 

 crossing. Both processes may even occur in the same germ cell, as 

 in the case of lata ruhricalyx. Tlie production of such mutants as 

 lata, is concerned with irregularities in the meiotic process, by which 

 a new chromosome group arises. If, on the other hand, Mendelian 



