The study of the variation of the ray flowers of Rudbeckia hirta (cone flower) was taken up during the summer of 1906, at the suggestion of Dr. L. H. Pammel. The object of the study was to determine 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.
Proceedings of the Iowa Academy of Science
©1907 Iowa Academy of Science, Inc.
"A Study of the Variation of the Number of Ray Flowers of Certain Compositae,"
Proceedings of the Iowa Academy of Science, 14(1), 89-106.
Available at: https://scholarworks.uni.edu/pias/vol14/iss1/9