A Quantitative Study of Variation in the Bracts, Rays, and Disk Florets of Aster Shortii Hook., A. novae-angliae L., A. puniceus L., and A. prenanthoides Muhl., from Yellow Springs, Ohio

Open Access
Publisher Website
Google Scholar
Abstract
Quantitative studies were made upon the bracts, rays, and disk florets of four species of Aster growing at Yellow Springs, Ohio. A close correlation was found between bracts and rays, and attributed to the fact that the rays are axillary to the bracts. The degree of imbrication of the bracts was observed to bear a relation to the number of empty bracts. Curves and "constants" were determined for the material of the four species studied. "Constants" determined for several individuals of A puniceus L. growing in identical surroundings indicated how great variations may exist in the variability "constants" of individuals. Studies upon successive collections from a single group of specimens of A. prenanthoides Muhl. showed that the number of bracts, rays, and disk florets all decrease continuously from the beginning to the end of the flowering season, and that the character of the curves and the position of their means and modes likewise change continuously. I wish to express my thanks to Prof. W. L. Tower for his kindly interest and helpful suggestion during the prosecution of these studies, and also for the revision of the manuscript