EMBRYO 
The fertilized egg divides transversely, producing al arge lower 
cell and small upper cell. As in Naias (Campbell, 1897, p. 26), 
Zannichellia (Campbell, |. c., pp. 27, 28), Zostera (Rosenberg, 1901, I; 
Hofmeister, 1852), and Potamogeton (Wiegand, 1900), the former 
divides no further, but subsequently increases vastly in size, develop- 
ing large vacuoles, and becomes the suspensor, which is thus in 
this case restricted to a single large, basal cell. 
I was unable to discover any stages between the two-celled pro- 
embryo and the twelve-celled stage—the latter represented in 
Pl. XIII, fig. 100. Murbeck, however, figures a three-celled stage 
in Ruppia rostellata, which I reproduce (Pl. XIII, fig. 98), showing 
two small cells, which may be called the “ embryo-cells,” arisen from 
the transverse division of the small upper cell; and also the basal 
large cell, namely, the suspensor-cell. Wille (1883) figures and 
also describes a similar stage in his work on the embryo of Ruppia 
rostellata. 
Wille has carefully followed the development of the proembryo 
in these early stages, and his observations and figures accord well 
with my slightly older embryos. His report of the succeeding 
divisions is briefly as follows: The lower of the two embryo-cells 
divides longitudinally, followed by a similar division in the same 
plane in the upper cell, making four cells in all; next, by longitudinal 
divisions in both segments, in a plane at right angles to the last, 
an eight-celled structure is formed. The embryo now consists, 
therefore, of two four-celled segments lying one over the other, 
and borne on a single large suspensor-cell (Pl. XIII, fig. 99.) 
It should be borne in mind that this suspensor cell is the basal 
segment resulting from the first division of the fertilized egg, and 
never again divides. In this connection it may be well to follow 
out the subsequent history of this peculiar suspensor before going 
into an account of the embryo proper. 
After the first unequal division in the fertilized egg-cell, the 
suspensor-cell becomes rapidly larger, and at the time when the 
two four-celled segments appear, as described above, it is much 
larger than these combined (PI. XIII, fig. 99). At the period shown 
in Fig. 100, when the embryo contains twelve cells, the suspensor- 
