A STUDY OF THE VARIATION OF THE NUMBER OF RAY 
FLOWERS OF CERTAIN COMPOSITAE. 
BY WINFIELD DUDGEON. 
The study of the variation of the ray flowers of Rudbeckia hirta 
(cone flower) was taken up during the Summer of 1906, at the sug- 
gestion of Dr. L. H. Pammel. The object of the study was to de- 
termine the amount of variation of the ray flowers, the variation for 
different localities, and any other facts that could be determined. 
Later, a study of Rudbeckia triloba and Helianthus grosse-serratus 
was taken up, with the same end in view, and that the different 
species might be compared. 
In all, 5,885 heads were counted, with a distribution as follows : 
TABLE No. 1. 
Distribution of the Heads Counted. 
Flower 
No. 
Heads 
Locality 
Collected by 
Date 
Rudbeckia hirta 
Rudbeckia 
triloba 
Helianthus 
grosse-serratus 
f 3,847 
558 
] 128 
3,161 
} 742 
f 1,296 
1 125 
I 1,171 
Total 
Ames, la. 
Center Point, la. 
8 miles southeast of 
Hedrick, la. 
Ames, la. 
Total 
Council Bluffs, la. 
Ames, la. 
E. R. Garner and 
writer 
D. C. Snyder 
Writer 
Class in Evolution 
of Plants 
Aug., Sept. 
Aug. 
July, Aug. 
Sept. 
Sept. 
Sept., Oct. 
Class in Evolution 
of Plants 
All of the heads of Rudbeckia hirta were counted by the writer. 
The heads of Rudbeckia triloba and Helianthus grosse-serratus 
were counted by a class in Evolution of Plants, at Iowa State 
college. Some of the Rudbeckia hirta plants grew in a dry, light, 
sandy soil, in a closely cropped pasture. All of the other plants 
grew in from average to good conditions. 
All of the heads were taken at random. No conscious selection 
was used. In nearly all cases, when a plant was taken, all of the 
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