Vol. 43 No. 11 
BULLETIN 
OF THE 
TORREY BOTANICAL CLUB 
NE 
NOVEMBER, 10916. 
The development of the embryo and seedling of Dioscorea villosa 
PEARL MABRY SMITH 
(WITH PLATES 31-34) 
INTRODUCTION 
According to the standard manuals, Dioscorea villosa L. is the 
only North American species of the Dioscoreaceae, a family that 
is mainly tropical and subtropical in distribution. Bartlett (1910), 
however, considers the name D. villosa at once a misnomer and 
a possible source of confusion and error, and proposes that it be 
dropped. In his classification, the Dioscoreae of the United 
States are referred to five separate species; the one treated in the 
present paper he calls D. paniculata Michx. 
The early discussions of the embryos and seedlings of members 
of this family are confined to the mature embryo and its behavior 
in germination, and were prompted chiefly by taxonomic con- 
siderations. Dutrochet (1835) says that the embryo of Tamus 
communis is at first globular, then pear-shaped; the slender part 
is the cotyledon, the swollen part the body of the embryo. He 
describes two cotyledons: the one, conical in form, remaining 
within the seed during germination; the other, so closely ap- 
plied to the globular part of the embryo that it is distin- 
guishable only after germination. The larger cotyledon per- 
sists until the middle of summer. Dutrochet also describes the 
structure of the aerial stem, whose fibro-vascular bundles are of 
the monocotyledonous type, but arranged in a ring. He thinks 
that this apparent mingling of monocotyledonous and dicoty- 
The BULLETIN for October (43: 505-544. pl. 27-30) was issued November 7, 1916. 
545 
