250 Campbell. — On the development 
is by no means invariably the case. In no case, however, are 
new archegonia developed. Arcangeli’s statement 1 that the 
chlorophyll is developed independently of the action of light 
was confirmed. Spores were placed in water and removed 
at once to a dark place, where they were allowed to remain 
undisturbed for a week. At the end of this time young plants 
were found developed in a perfectly normal manner. They 
were slightly smaller, and the amount of chlorophyll may 
have been possibly rather less than in plants grown under 
normal conditions, but the difference was very slight. 
The Embryo. 
The fertilized oosphere is not perfectly spherical, but more 
or less elongated transversely, and before the first division is 
completed this is strongly marked (PI. XIV, Figs. 1, 2). The 
first wall (basal wall) in the young embryo is approximately 
parallel to the axis of the archegonium, and divides the germ- 
cell into two equal cells (PL XIV, Fig. 2). The youngest 
case where the completed division was seen was forty-six 
hours after the commencement of germination, but it is not 
improbable that it may occur somewhat earlier, as embryos 
only two hours older were observed in some cases (PL XIV, 
Figs. 6-8) to be already divided into numerous cells. 
Of the two primary cells, one, as in the Polypodiaceae, gives 
rise to the first leaf and stem, the other to the root and foot. 
Of course, as the structure of the prothallium is radial, it is 
impossible to speak of an anterior and posterior cell at this stage. 
The second or quadrant-wall (Pl. XIV, Fig. 3 11) follows as 
in other Pteridophytes, and divides the embryo into quadrants, 
the two upper being as a rule evidently larger than the lower 
ones. 
In regard to the following divisions there is much difference 
of opinion, at least for Marsilia , which probably does not differ 
materially from Pilularia . Hanstein claims that the first wall 
in the embryo separates at once the stem and root, and that 
1 1. c. } p. 336. 
