Dec, 1919] Dieciousness in Thalictrum Dasycarpum 2i7 



No. 18. A carpellate plant with 4 bisporangiate flowers; 3 flowers with 1 stamen 

 each, and 1 flower with 2 stamens. 



No. 19. A carpellate plant with 4 bisporangiate flowers, each flower with 1 stamen. 



No. 20. A carpellate plant with 2 bisporangiate flowers, each with 1 stamen. 



No. 21. A carpellate plant having among its ntimerous carpellate flowers 1 bispo- 

 rangiate flower with 1 stamen. 



No. 22. A pure carpellate plant. 



If one were inclined to take the time, there is no doubt but 

 that intermediates of almost any conceivable degree of expres- 

 sion of maleness or femaleness could be found. The careful 

 study of individual plants is, however, very tedious, since the 

 larger individuals have great inflorescences with flowers running 

 into the many hundreds. Apparently intermediates are every- 

 where common in Thalictrum dasycarpum. Around Columbus, 

 Ohio, they are abundant. 



According to Overton* Thalictrum purpurascens has 24 

 chromosomes in the gametophyte and 48 in the sporophyte. 

 The species studied was probably either Thalictrum dasycar- 

 pum Fisch. & Lall. or Thalictrum revolutum DC, or both. 

 Now one might consider that the complex sexual expression of 

 Thalictrum dasycarpum was due to the presence of multiple 

 sex factors distributed in a large number of the chromosomes. 

 If there were a half dozen or so allelomorphic pairs of sexual 

 factors and if the number of allelomorphs of one nature or 

 the other determined the degree of intensity and the constancy 

 of sexual expression in some such way as multiple color factors 

 or m.ultiple size factors, the resulting diversity of sexual expres- 

 sion might be something like what actually takes place. But 

 such an hypothesis would after all not explain the facts in the 

 case. For one can find the same diversity of distribution among 

 the various branches of certain bisporangiate individuals as 

 exists among the individuals themselves. 



The following examples will indicate the complexity of 

 sexual expression as found in intermediate individuals studied. 

 In the tabulations the main lateral branches coming from the 

 central axis of the inflorescence are roughly considered as 

 equivalent parts and the terminus above the larger branches is 

 considered as one branch. The plants listed were mainly stam- 

 inate in nature but showed considerable carpellate expression. 

 All the branches had large numbers of pure staminate flowers. 



* Overton, J. B. On the Organization of the Nuclei in Pollen Mother cells of 

 certain Plants with Especial Reference to Permanence of Chromosomes. Ann. of 

 Bot. 23 : 19-61, 1909. 



