556 SMITH: DIOSCOREA VILLOSA 
plant is a climber, however, and the structure of the root might be 
explained on that ground, thus losing its phylogenetic significance, 
SUMMARY 
1. The plane of the first division of the egg is oblique. 
2. A spherical four-celled proembryo is formed. 
3. The first secondary leaf is the first organ of the embryo to 
be differentiated. The growing point of the stem consists, up 
to the time of germination, of a group of cells in the axil of the 
first secondary leaf. Both structures are lateral in origin. 
4. No “cotyledonary ring’ was observed. The cotyledon 
originates in a terminal position. 
5. No structure which is in any way comparable to a second 
cotyledon is present; the sheath which is described as covering 
the plumule in other Dioscoreaceae is wanting. 
6. Abundant endosperm is present in the secd. 
7. The growing point of the stem begins to give off secondary 
leaves soon after the seed germinates. 
8. The root of the seedling is tetrarch; the hypocotyl is 
polyarch. 
Sincere thanks are due to Professor I. F. Lewis, at whose 
suggestion the investigation here reported was begun, and to 
Professor C. E. Allen, under whom it was continued, for helpful 
advice and criticism. : 
UNIVERSITY OF» WISCONSIN 
LITERATURE CITED 
Bartlett, H. H. 1910. Source of the drug Dioscorea, with a con- 
sideration of the Dioscoreae found in the United States. U. S. 
Dept. Agr. Bur. Pl. Ind. Bull. 189. 
Beccari, O. 18700. Nota sull’ embrione delle Dioscoreacee. Nuov.- 
Beccari, O. 1870b. Nota sul T richopodium zeylanicum. Nuov. 
Giorn. Bot. Ital. 2: ¥g-10. 31.3, 
Bucherer, E. 1889. Beitrage zur Morphologie und Anatomie der 
Dioscoreaceen. Bibliotheca Botanica 16. : 
Campbell, D.H. 1897, A morphological study of Naias and Zannt- 
chellia. Proc. Calif. Acad. Sci. III. 1: I-61. pl. 15. : 
Campbell, D.H. 1898. The development of the flower and embryo in 
Lilaea subulata, H. B. K. Ann. Bot. 12: 1-28. pl. 1-3. 
