No. 599] SHORTER ARTICLES AND DISCUSSION 



091 



was grown, this summer from what seemed to be the most promis- 

 ing plant of the F 3 (15.53a). This culture was from seed ger- 

 minated in Petri dishes and was complete, since the residue of 

 ungerminated seeds were empty of contents. From 764 seed- 

 like structures 668 seedlings appeared, but there was at once a 

 large mortality among weaklings most of which were unable to 

 free their cotyledons from the seed coats. Only 558 seedlings 

 lived to be potted and a further mortality reduced the number 

 that was set out in the garden to 549. Of these plants 198 as 

 rosettes presented characters of Lamarckiana while 351 developed 

 rosettes for the most part with narrower leaves suggestive of 

 franciscana. All of the shoots from the 198 Lamarckiana-like 

 rosettes have shown Lamarckiana characters of foliage, inflo- 

 rescence, and flowers but about one fourth of the plants seem 

 likely to persist this summer as rosettes. The group of neo- 

 Lamarckiana in the F 4 generation is therefore large constituting 

 about 36 per cent, of the total number of plants in the culture. 



In the group of nco-Lamarckiana there is some variation, but 

 the best plants are so close to the Lamarckiana of De Vries that 

 I can only distinguish them by small plus or minus expressions 

 of a few characters. Thus the central shoot is not so strongly 

 developed proportionally to the side branches. The leaves are 

 a little broader. Sepal tips do not spread so widely. Buds 

 may not be quite so stout. The pubescence is somewhat heavier 

 over certain portions of the plants. Time will tell whether even 

 these small differences can be eliminated by judicious selection 

 through succeeding generations. 



It is of course not enough for critical bearing on De Vries 's in- 

 terpretation of the behavior of Lamarckiana that a hybrid should 

 be synthesized taxonomically similar to it. Such a hybrid must 

 also show a behavior parallel to Lamarckiana in its essential fea- 

 tures. The two striking peculiarities in the breeding habits of 

 Lamarckiana are (1) its ability to produce two types (twin 

 hybrids) in the F 1 when mated to certain other species, and (2) 

 its peculiarity of throwing through successive generations the 

 same types of " mutants" in small, fairly constant proportions. 

 Late in the season of 1915 reciprocal crosses were made between 

 neo-Lamarckiana (15.53a) and plants of biennis and biennis 

 (Chicago), forms which De Vries has used in his studies on twin 

 hybrids from Lamarckiana. The conditions were not favorable 

 for the technique of crossing and I am repeating the experi- 



