eR ge a ee EN Te One eee 
a ee es 
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1900] DEVELOPMENT OF THE EMBRYO-SAC 39 
far wrong in making this interpretation. The half-grown embryo 
shown in fig. 27 was the oldest stage obtained. At this time 
only the epidermis was differentiated, while the plerome is 
scarcely distinguishable. At the upper end of the figure may 
be seen the cotyledon; and at one side the plumule, arising in a 
depression at the apex of the hypocotyl. 
Schaffner and Campbell both find that no division takes place 
in the enlarged basal cell after its formation. There is certainly 
none in Potamogeton. Probably the observation of Hanstein 
that such a division does take place in Alisma was inaccurate. 
That such a division does occur in some monocotyledons, how- 
ever, is a well established fact as shown by Coulter ™ in his 
studies of Lilium. In this plant the basal cell undergoes both 
longitudinal and transverse divisions. The process in Potamo- 
geton does not differ essentially from that in Sagittaria and Naias, 
as given by the two authors cited above. ~The subbasal cell in 
Naias divides by transverse walls into three instead of two cells, 
of which the upper forms several cells, while the lower remains 
undivided. In Sagittaria the subbasal cell divides also once 
more than in Potamogeton, and the uppermost daughter cells 
here again form considerable tissue. 
Canna Indica L. 
THE HYPODERMAL CELL AND ARCHESPORIUM. 
Canna represents still a third type of the monocotyledonous 
embryo- -sac, differing in method of development from Lilium 
Convallaria, and also from Potamogeton. 
The hypodermal cell very soon divides into two parts by 
means of a periclinal wall (fig. 29). The upper cell then by 
repeated anticlinal division rapidly forms a layer of about nine 
cells directly above the future embryo-sac. This layer together 
with the epidermis constitutes the wall of the sporangium, and 
remains unchanged until finally displaced by the embryo-sac 
beneath. 
** COULTER, J. M.: Contributions to the life-history of Zz/ium Philadeiphicum — 
The embryo-sac and associated structures. Bot. Gaz. 23 :413- 1897. 
