Feb., 1918] Sexual Dimorphism 123 



part of sexual phenomena becomes unexplainable and con- 

 tradictory. The presence of allosome difference in certain 

 sexual individuals does not make it necessary for us to amend 

 the proposition that sexuality either male or female is a state 

 or condition and not a mendelian factor or set of factors. 



For the convenience of those who wish to make a study 

 of our more common or interesting species, the following short 

 list is given as an index to the general condition usually present 

 in monecious and diecious plants: 



Four genera to illustrate the relation of diecious to 

 bisporangiate species — Thalictrum, Rumex, Acer, Fraxinus. 



Thalictrum clavatum DC. Flowers bisporangiate. 

 Thalictrum dasycarpum Fisch. & Lall. All gradations of bisporangiate 

 to staminate and carpellate flowers on the same plant. 



Thalictrum dioicum L. Plants diecious. 



Rumex crispus L. With bisporangiate flowers and carpellate 

 flowers containing prominent vestigial stamens on the same plant. The 

 stigmas are much branched. 



Rumex altissimus Wood. Monecious. The carpellate flowers have 

 six vestigial stamens; the staminate flowers have a vestigial g}^necium 

 with three slightly branched stigmas. 



Rumex acetocella L. Diecious. The staminate flower has a minute 

 vestigial gynecium with three, unbranched, vestigial stigmas; the 

 carpellate flower apparently has no vestigial stamens; the stigmas are 

 much branched. 



Acer platanoides L. Imperfectly diecious. Some carpellate trees 

 have staminate and some staminate trees carpellate flowers; both kinds 

 of flowers have prominent vestiges of the opposite organs. The flowers 

 have large petals and a prominent nectar disk. 



Acer saccharinum L. Diecious. Carpellate flowers with vestiges of 

 stamens; staminate flowers with vestigial g\mecia. Some plants 

 occasionally have bisporangiate flowers. The petals are absent. 



Acer negundo L. vStrictly diecious. The flowers are much reduced 

 and have no vestiges of the opposite organs. 



Fraxinus cuspidata Torr. Flowers bisporangiate with a calyx and 

 corolla; very fragrant. 



Fraxinus americana L. Strictly diecious. Flowers small without 

 corolla but with a small calyx; no vestiges of the opposite sporophylls. 



