THE EMBRYOLOGY OF ALYSSUM.* 
LUMINA COTTON RIDDLE. ra 
(WITH PLATES XXVI-XXVIII) 
Tue following study of Alyssum macrocarpum was begun late 
in October when a large and thrifty plant was brought into the 
greenhouse. Cuttings were made which began blooming about 
the holidays and a constant supply of material was thus fur- 
nished, | 
My original intention was to study Capsella bursa-pastoris and 
to verify or modify the account of its embryonic development, 
since Capsella has usually been taken as a type for the dicotyls. 
While Hanstein’s method of studying the embryo by squeezing 
it from the ovule and staining with iodine might appear incapa- 
ble of yielding any results of a detailed character, it seems 
nevertheless in his hands to have given rather accurate results. 
The close relationship of Alyssum to Capsella, and the 
resemblance in embryonic development, which was evident from 
the first comparison with Hanstein’s familiar figures, became a 
constant stimulus to careful and accurate investigation. While 
I am not wholly positive as to the invariability in the formation 
of certain portions of the young embryo plant, the most of my 
work points to a certain definite course of development, though 
there are sometimes remarkable variations. 
My sincere thanks are due to Professor W. A. Kellerman and 
Mr. J. H. Schaffner for their continued encouragement and 
valuable suggestions. 
METHODS. 
Greenhouse plants did not seed profusely, probably because 
there were no insects present to assist in pollination. Before 
killing the material, the sepals, petals and stamens were removed, 
*Contributions from the Botanical Laboratory of Ohio State University. V- 
[ NOVEMBER 
