SMITH: DIOSCOREA VILLOSA 547 
from which it is pushed aside by the development of the lateral 
true cotyledon. The so-called second cotyledon is, he thinks, 
merely a sheath. Both cotyledon and sheath are developed, 
however, according to Solms-Laubach, from a ring-shaped pri- 
mordium. : 
Bucherer (1889) points out the additional fact that in Tamus 
not only the first secondary leaf, but all the secondary leaves, 
have similar sheaths. He also describes the anatomy of the 
mature embryo, and the processes of germination and of tuber 
formation. His account of the germination of the seed does not 
differ from the accounts of his predecessors. 
MATERIAL AND METHODS 
Material was collected in the vicinity of Madison, Wisconsin, 
at intervals of two or three days during the months of June, 
July, and August, 1913 and 1914. The flowers were fixed entire; 
when the ovules became sufficiently large, they were removed 
from the capsules before fixing. Later, the embryos were dis- 
sected out of the young seeds and then fixed. Difficulty was 
experienced in inducing the seeds to germinate, but germination 
was finally secured by keeping the seeds in soil out of doors all 
winter and bringing them into the greenhouse in the spring. 
Strong and medium chrom-osmic-acetic acid solutions were 
used for all material of the embryo-sac and embryo which was to 
be sectioned; the stronger solution proved the more satisfactory. 
For embryos to be mounted in toto Carnoy’s solution was used; 
for the seedling, a chrom-acetic acid solution, containing three 
tenths of a gram of chromic acid and seven tenths of a gram of 
acetic acid in each hundred grams of the solution, gave good 
results. The usual methods of hardening and embedding in 
paraffin were followed. Microtome sections were cut from five to 
seven microns thick. 
Material containing embryo-sacs or early embryonic stages 
was stained with Flemming’s triple stain. For the study of the 
later stages in embryo-development, Heidenhain’s iron-alum- 
haematoxylin gave the best results. Some of the mature embryos 
were stained in toto with Delafield’s haematoxylin. Staining 
with safranin and Lichtgriin proved useful in differentiating the 
tissues of the seedling. 
