Dec, 1919] Dieciousness in Thalictrum Dasycarpum 31 



reduced and multiplied in the inflorescence until the cluster is 

 very complex when compared with a species having single 

 flowers terminating leafy branches. Thalictrum has progressed 

 far toward the complete segregation of the sporophylls, some 

 species, as mentioned above, being diecious with few if any 

 intermediates. Overton found true parthenogenesis in T. 

 purpurascens both when growing in an artificial environment 

 and also in the field. There is probably no question as to the 

 presence of parthenogenesis in the species; nevertheless, inves- 

 tigators along these lines should make a careful study of the 

 plants employed, otherwise self-pollination may be taking place 

 in individuals which were assumed to be monosporangiate 

 simply because the manuals describe them in general terms as 

 being diecious. 



Among the Cycadophyta, the more primitive Bennettitales 

 contain species with bisporangiate flowers while the specialized 

 modern Cycadales, which appear to have been derived from the 

 same primitive stock if not directly from them, have monospor- 

 angiate flowers and are diecious. 



The living conifers are mostly monecious as for example, the 

 Pinaceas and the lower Juniperaceae, like Thuja and Cham^ecyp- 

 aris, while the extremely specialized genus, Juniperus, with its 

 remarkably modified carpellate cone, is usually diecious. 



Monocotyls. 



Among the lower Helobiae, Echinodorus cordifolius (L.) has 

 bisporangiate flowers while its near relatives of the genus 

 Sagittaria are monecious or sometimes apparently diecious. 

 The extremely specialized species, Vallisneria spiralis L., plainh'- 

 belonging to the same group, is diecious. 



Some of the lower apocarpous palms have bisporangiate 

 flowers, while other species, like Phoenix dactylifera L., have 

 advanced to a diecious condition but show prominent vestiges 

 of the opposite set of organs in both the staminate and carpellate 

 flowers. 



Among the grasses, Atheropogon and Bouteloua have 

 bisporangiate flowers while the related Bulbihs dactyloides 

 (Nutt.) is diecious. 



The lower lilies are bisporangiate while among the special- 

 ized forms diecious species occur, like Smilax sp. and Chamae- 

 lirium luteum (L.) 



