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1901} OVULE AND EMBRYO OF POTAMOGETON 343 
Wiegand? demonstrated a two-celled row for P. foliosus, but 
found the fate of the two cells somewhat unusual. He says, 
“the first division of the archesporial cell is immediately fol- 
lowed by a second nuclear division in each of the daughter cells, 
but without the formation of a wall between the two nuclei. 
The upper of these two cells soon perishes, while the lower goes 
on through various phases forming at last the complete embryo 
sac.” 
In P. natans some irregularity appears in the number of cells 
of the axial row, but it is always more than two, brought about 
by the division of one or both daughter cells of the primary 
sporogenous cell. The early stages of the division of the sporog- 
enous cell are shown in figs. g-7._ In the stage shown in fig. 8, 
the chromosomes have passed to the poles, the spindle fibers are 
still intact, and the cell plate is clearly marked. A spindle is 
also formed in each daughter cell (fig. 9). It is at this point 
that the irregularity mentioned above appears. That a spindle 
is not always formed in each cell may be inferred from fig. 77, 
where the lower cell shows by its size, age, and nucleus that it is 
the functioning megaspore. The middle cell, its sister cell, is 
being resorbed along with the upper cell. The spindle shown 
in fig. ro indicates that the two resulting potential megaspores 
will lie side by side. The preparations referred to thus far do 
not show any completed four-celled axial row, but they do show 
several three-celled rows, with spindles to indicate four poten- 
tial megaspores. The spindle in the upper cell of the axial row, 
in both cases shown, is transverse rather than longitudinal. 
The germination of the megaspore—The divisions leading to 
the ante-fertilization stage of the gametophyte appeared perfectly 
regular and normal, although Wiegand} states that in P. pauciflorus 
both egg- apparatus and antipodals were somewhat abnormal. 
He says, “although the normal number of cells in each was 
present, they were formed irregularly. The polar nucleus and 
? WIEGAND, Karu M.: doc. cit. 32. 
3 WIEGAND, Karu M.: Notes on the embryology of Potamogeton. Bot. GAz. 
25: 116-117, 1888 
