1915.] PURE SPECIES OF OENOTHERA. 17 



cytological evidence that the first mitosis in the zygote of a higher 

 plant is ever a differential division. To the writer the situation 

 indicates that one or both of the two species is heterozygous and that 

 for this reason classes of gametes are formed, appropriate combina- 

 tions of which give the twins and triplets. No data has been pub- 

 lished respecting the sterility of these two species, either of pollen 

 or ovules, and nothing of seed abortion. An understanding of the 

 genetic constitution of the species is likely to be a difficult matter, 

 but it does not seem probable that both are pure. 



What shall be said of the probable purity of the plants of 

 (Enothera and Raimannia with which MacDougal worked in his ex- 

 periments designed to create new species by the injection of certain 

 fluids into the ovaries. The parent material was reported to breed 

 true, but the cultures were small and not long continued and there is 

 no reason to suppose that a complete germination of the seeds was 

 obtained. No information is given on the fertility of the species 

 either with respect to the abortion of gametes or the proportion of 

 good seeds. The material was not tested by cross breeding with 

 other forms (the purest known) to determine whether the F^ hybrids 

 were uniform, a most necessary test in the establishment of a stock 

 as homozygous. Thus from our present viewpoint we cannot 

 accept MacDougal's conclusion since the probabilities are very great 

 that the new types which appeared in his cultures were produced not 

 as the result of the injections but because of the genetic impurity 

 of the plants themselves. 



In the above discussion the writer has taken definitely a Men- 

 delian attitude in sympathy with the criticisms of Bateson and the 

 studies of Heribert-Nilsson ('12) and of Renner ('14). There are 

 constant suggestions of order in the phenomena of inheritance 

 among the Oenotheras which while they may not fall into simple 

 schemes of Mendelian notation nevertheless do indicate system even 

 though masked by complexities. That the complications at least in 

 great part are due to the genetic impurity of the Qinothera material 

 which has been so far the subject of study is the writer's belief. 

 The difficuhies that surround the analysis of (Enothera inheritance 

 are probably in very large measure due to the extraordinary amount 

 of sterility, gametic or zygotic, or both, that is present in the group. 



