548 SMITH: DIOSCOREA VILLOSA 
THE EMBRYO-SAC 
Two anatropous ovules are borne in each cell of the three- 
celled ovary and are pendulous on rather short funiculi. Beccari 
(1870b) figures the ovules in Trichopus zeylanicus as turned towards 
the axis of the pistil, but in Dioscorea villosa they are turned away 
from the axis. 
At the time when the embryo-sac is fully organized (Fic. 1), 
the three antipodal cells have already begun to degenerate and 
fusion of the polar nuclei has taken place. Before the egg divides, 
its cytoplasm is highly vacuolate, and the nucleus occupies a 
position either approximately in the center or at the distal end 
of the cell. Both synergids persist, at least in some cases, until 
after the first division of the egg. When the embryo is somewhat 
older, only one structure is found beside it which I take to be a 
synergid. This structure (FIG. 5, s) sometimes forms a beak with 
faint longitudinal striations, which extends into the micropyle 
and corresponds closely in form and appearance with the “ Faden- 
apparat”’ first described by Schacht (1856). 
THE EMBRYO 
The first division of the egg takes place only after several 
nuclear divisions have occurred in the endosperm. In an embryo- 
sac containing a two-celled embryo a count of the endosperm 
nuclei shows that five divisions have taken place, and the general 
appearance of the endosperm in other similar cases indicates that 
about the same number of divisions has occurred. In all cases 
observed, the plane of the first division of the egg is oblique 
(FIG. 2), approaching in a few instances the vertical (Fic. 4) oF 
the horizontal (Fic. 5). The corresponding division is in an 
oblique plane in Tulipa Gesneriana (Ernst, 1901), and occasionally 
in Avena fatua (Cannon, 1900); and A glaonema (Campbell, 1900). 
But in most monocotyledons, so far as has been reported, the 
plane of this division is transverse, as for instance in such forms 
as Sagittaria variabilis (Schaffner, 1897), Lilaea subulata (Camp- 
bell, 1898), and Lilium philadelphicum (Coulter, 1897). A trans- 
verse first division is found also in Tamus communis (Solms- 
Laubach, 1878), another of the Dioscoreaceae. The cells pro- 
