The Ohio Journal ox Science 



Vol. XX DECEMBER, 1919 No. 2 



DIECIOUSNESS IN THALICTRUM DASYCARPUM.* 



John H. Schaffner. 



In the search for further Hght on the nature of dieciousness, 

 the writer made some observations on ThaHctrum, as repre- 

 senting a genus of plants quite low in the evolutionary scale yet 

 showing considerable specialization. The Ranunculacese, among 

 which the meadow-rues are included, are normally bisporan- 

 giate plants and the lower species of ThaHctrum are also 

 bisporangiate, as for example, ThaHctrum clavatum DC. and 

 ThaHctrum alpinum L. ThaHctrum clavatum shows plainly 

 that the ancestral type of the genus had the normal lateral 

 stamens and terminal carpels so characteristic of Anthophyta, 

 altho in the specialized species as will appear below there is 

 no definite position for either stamens or carpels in the inter- 

 mediate type of flowers. ThaHctrum dsycarpum Fisch. and 

 Lall. and ThaHctrum revolutum DC. are among the diecious 

 species with many intermediate individuals, while ThaHctrum 

 dioicum L. and other species are normally strictly diecious. 



In ThaHctrum dasycarpum there is no apparent sexual 

 dimorphism between the staminate and carpellate plants except 

 in the sporophylls themselves and even the stamens and carpels 

 have an unusual similarity of appearance before the filaments 

 elongate. 



A considerable per cent of the individuals are apparently 

 strictly staminate or carpellate and from these extremes, inter- 

 mediates grade through all degrees up to individuals which pro- 

 duce nearly an equal number of stamens and carpels. Next to a 

 pure staminate plant may be one completely staminate except 

 that one flower has one normal carpel. A single sporophyll with 

 female expression among thousands with male expression! 

 Or there may be an individual having all carpellate flowers but 

 one of these flowers has a single stamen. The stamens and 



Papers from the Department of Botany, The Ohio State University, No. 118. 



25 



