44° 



BOTANICAL GAZETTE 



[DECEMBER 



among ii8 plants of the cross. As a matter of fact, the significance 

 of ratios in Oenothera can be maintained only with great caution, 

 in view of the enormous elimination of gametes during matura- 

 tion and the subsequent failure of large classes of zygotes to 

 develop. Nevertheless, the absence or almost complete absence 

 of a strong zygote such as f . typica in the progenies of mut. angusii- 

 folia and mut. angustifoliaXi- typica is strong evidence for the view 

 that the composition of the progeny among the mass mutating 

 strains is conditioned by the female gametes. The failure of a 



TABLE IV 



Analysis or Fi chltuees of mut. angustifolia, Lexington E-s-208, self-pollinated 



AND EECIPROCALLY CROSSED WITH F. typica, LEXINGTON £-5-229 (tHE 

 PLANT WHOSE PROGENY IS ANALYZED IN TABLE III) 



The mutation was a sister plant of the typica plant with which it was crossed; for 

 position in pedigree see table 11, culture i from Lexington E-5 



* The 651 seeds were from 11 capsules, containing respectively sr, 75, Sit 62, 44, sg, 82, loi, 46, 33, 

 and 45 seeds. 



t The 199 seeds were from 3 capsules, containing respectively 73, 47, and 79 seeds. 

 X The 182 seeds were from. 2 capsules, containing respectively 79 and 103 seeds. 



class of strong zygotes to appear has much greater evidential 

 value than any fluctuation in the proportion of weak zygotes. 

 From other sources the evidence is unusually strong that the female 

 and male gametes of 0. pratincola are not equivalent, and that many 

 characters are not carried by the male gametes. 



In conclusion: mut. angustifolia ordinarily gives a progeny 

 containing nearly loo per cent of f. typica; in a strain exhibiting 

 mass mutation many of the typica plants are replaced by mutations 

 of the characteristic group. Presumably other individuals of 

 mut. angustifolia could be found which would be less mutable than 

 the one tested, just as different individuals of f . typica show widely 



