Varietäten, Descendenz, Hybriden. 53 



but the best plants are so close to the Lamarckiana of de Vries, 

 that they can only be distinguished by sraall plus or minus 

 expressions of a few characters. It is of course not enough for 

 critical bearing on de Vries's interpretation of the behavior of 

 Lamarckiana that a hybrid should be synthesized taxonomically 

 similar to it. Such a hybrid must also show a behavior parrallel 

 to Lamarckiana in its essential features. The two striking peculi- 

 arities in the breeding habits of Lamarckiana are (1) its ability to 

 produce two types (twin hybrids) in the F^ when mated to certain 

 other species, and (2) its peculiarity of throwing through successive 

 generation the same types of „mutants" in small, fairly constant 

 proportions. 



Grosses between biennis X neo- Lamarckiana (and reciprocal) 

 appear to have given twin hybrids and it should be said that the 

 two groups were recognized and separated when ihe plants were 

 in the rosette stage and that they consistenly presented differences 

 throughout all stages of their development. 



With respect to the ability of neo- Lamarckiana to throw 

 mutants a most interesting Situation is presented by its behavior 

 this Summer in the fourth generation. In throwing a large progeny 

 of a type very differing from the parent Fg-plant, neo-Lamarckiana 

 in the F4 exhibited a behavior with strong resemblance to what 

 Bartlett has described as massmutation. 



The conditions in sterility in neo-Lamarckiana are likely to 

 bear directly on the peculiarities of its behavior in comparison 

 with that of de Vries's plant. The writers hybrids agree with 

 Lamarckiana in having pollen about one half sterile, but the F3- 

 parent plant of this years cultures showed seeds 87 per cent 

 fertile while the seed fertility of Lamarckiana is much lower, 

 being reported as from 26—46 per cent. May not the mass Varia- 

 tion of neo-Lamarckiana in the F4 be correlated with its very 

 much higher seed fertility? 



The results show that Lamarckiana -\\^e forms of Oenothera 

 may be synthesized by simple crosses between wild species pro- 

 vided the parent species are selected -Ä^ith care. The writer believes 

 that as the Isolation of Oenothera types proceed a number of diffe- 

 rent crosses will be found to give similar results, but this is the 

 first successful combination that the writer has been able to study 

 experimentally. He should be the last to suggest that the particular 

 races or species which gave his neo-Lamarckiana have been the 

 actual parents of the strains oi Lamarckiana cultivated by de Vries. 

 It is remarkable that his results have proved so satisfactory ; no 

 doubt other species crosses may sometime be made which will 

 give hybrids as close or even closer to Lamarckiana-\\ke hybrid 

 may have for the problem of the origin and Status of Oenothera 

 Lamarckiana is likely to be a clearer understanding of how an 

 obviously impure species, neo-Lamarckiana, may arise, a species 

 which seems likely to present a breeding behavior parallel to that 

 of Lamarckiana, and most important of all the significance of 

 sterility in the working out of these results. 



M. J. Sirks. (Wageningen). 



Trelease, W., Naming American hybrid oaks. (Proc. Amer. 

 Philos. Soc. LVI. p. 44—52. pl. 1-3. May, 1917.) 

 Forty reputed hybrids of Quercus in the United States are 



