THE DICLINOUS FLOWERS OF IV A GANTHIIFOLIA , NUTT. 
BY CLIFFORD H. FARR. 
Relatively few of the Compositae have been studied throughout their 
whole life history. Most investigations have dealt with the varied 
expressions of a single structure, such as vascular anatomy, style, etc., 
in various genera of this family. However valuable such research it 
cannot replace the more intensive study of a single species. Only by 
this latter method can 'the different morphological structures be satis- 
factorily interpreted and relationships established. 
Probably no group of Angiosperms displays a wider range of dicliny. 
In some species all the flowers are perfect ; in a few there are pistillate 
and staminate individuals; while the remaining forms display almost 
all possible intermediate conditions. Uexkull-Gyllenband j(14) and 
others have called attention to the fact that several forms: of dicliny 
may occur within a single species. 
This study was undertaken in the hope of throwing some light upon 
the organography of the capitulum of the Compositae. Iva xanthiifolia , 
Nutt was selected since it possesses both pistillate and staminate flowers 
in the same head. The former are always marginal and the latter are 
always central thus displaying a; very stable condition with respect to 
the differentiation of sex. 
The material was collected during the summer of 1911 in the vicinity 
of the Macbride Lakeside Laboratory on West Okoboji Lake in Iowa, 
The writer is indebted to Professor R. B. Wylie for many helpful sug- 
gestions and for his kindness. in directing the work. 
INFLORESCENCE. 
The flowers of Iva xanthiifolia, Nutt, are arranged in the capitulum 
in concentric cycles of five flowers each (fig. 1),- the members of suc- 
cessive whorls alternating. The outer cycle consists of five pistillate 
flowers, each in the axil of a large involucral bract. The staminate 
flowers, numbering 11 to 23 in each head, make up the! remaining whorls. 
Developmeht is in acropelal succession, often leaving the youngest inner 
