No. 599] SHORTER ARTICLES AND DISCUSSION 



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although generally stronger, larger-leaved, and with considerable 

 variation in flower size. It should be noted that no forms similar 

 to the parent biennis were present ; this type of segregate seem- 

 ingly is either not produced or appears but rarely. 



The conditions of sterility in neo-Lamarckiana are likely to bear 

 directly on the peculiarities of its behavior in comparison with 

 that of De Vries's plant. My hybrids agree with Lamarckiana 

 in having pollen about one half sterile, but the F 3 parent plant of 

 this year's cultures showed seeds 87 per cent, fertile while the 

 seed fertility of Lamarckiana is much lower, being reported by 

 De Vries in extensive experiments as from 34.5-46 per cent, and 

 for two lines of mine running in tests 26-30 and 32-36 per cent., 

 respectively. The variation noted by De Vries is believed by 

 him to depend upon whether or not the plants are heavily 

 manured. The question at once arises may not the mass varia- 

 tion of neo-Lamarckiana in the F 4 be correlated with its very 

 much higher seed fertility ? What would happen if neo-Lamarck- 

 iana should develop a greater degree of seed sterility or if some 

 lines should be segregated with seed sterility approaching that 

 of De Vries's Lamarckiana? Would the plants eliminated come 

 from among the neo-Lamarckianas or would they come from the 

 assemblage of variants from this parent type? Should they 

 come from the variants, as seems to me probable since neo- 

 Lamarckiana is a sturdy plant, then a condition might be reached 

 where the variants would appear rarely or in small proportions 

 and this would parallel exactly the present behavior of De Vries 's 

 Lamarckiana in throwing its ' ' mutants. ' ' I shall watch intently 

 for indications in my cultures of increased seed sterility and 

 among my plants of neo-Lamarckiana select steadily towards the 

 higher degree exhibited by Lamarckiana. It is interesting that 

 the last stages in the experimental synthesis of a Lamarckiana- 

 like hybrid should be concerned chiefly with selection towards a 

 definite degree of seed sterility. 



CEJnothera neo-Lamarckiana illustrates clearly my concept of 

 an impure species of Oenothera. 5 It is a plant that breeds true 

 in a proportion of its offspring but is heterozygous since it de- 

 velops varied types of gametes as proved by the assemblage of 

 offspring which differ sharply from the parent plant, and further 

 indicated by its behavior in producing twin hybrids. The facts 

 of a high degree of pollen sterility (about 50 per cent.) together 

 5 Davis, B. M., "The Test of a Pure Species of (Enothera," Proc. Amer. 

 Phil Soc, LIV, 226-245, 1915. 



