1918] DUDGEON—RUMEX CRISPUS 307 
advanced case observed, the 2 megaspore mother cells had fully 
enlarged and were in prophase of the heterotypic mitosis (fig. 24). 
They were separated by a crushed cell of equal length, which may 
have been a megaspore mother cell, but more probably was only a 
vegetative cell that became so crushed that it could not divide, and 
was forced to elongate with the enlarging mother cells. 
The megaspore mother cell enlarges and elongates considerably, 
then undergoes two successive divisions to form a tetrad of cells 
(fig. 28). Apparently this division is a true reduction, for all the 
stages seem to be normal, and at diakinesis there are 32 pairs of 
chromosomes (fig. 26). While an accurate count of the chromo- 
somes could not be made on the spindle, careful estimation indicates 
that the number still is 32 (fig. 27). In the vegetative cells the 
spindle is shorter, and proportionally much broader, and while 
the chromosomes are too small and too densely massed to be 
definitely counted at any stage, they clearly are more numerous 
than in the megaspore mother cell; I could only estimate that 
there are about twice as many, that is, 64. 
Wall formation follows each of the reduction mitoses. The 
first wall usually divides the mother cell a little above the center 
(fig. 30). The second wall is usually near the outer end of the 
inner cell (figs. 29, 30), although in the best preparation found 
(fig. 28) the cell is nearly equally divided. The wall in the outer 
cell is always longitudinal, instead of transverse (fig. 28). There 
is some irregularity in the sequence of the homoiotypic division; 
usually the inner cell divides first (fig. 30); sometimes the divisions 
are simultaneous (fig. 28); and in one case the outer cell was the 
first to divide. 
The inner megaspore functions, and the others quickly degener- 
ate (fig. 29). The third megaspore rarely forms a normal cell, 
and is usually the first to degenerate (figs. 31, 33). The outer cell 
may degenerate before it has a chance to divide, or the 2 mega- 
spores may degenerate before they are separated by a wall (fig. 31). 
Empryo sac.—The functioning megaspore rapidly elongates 
and develops a large vacuole at each end, with the nucleus centrally 
placed (figs. 33-35). The daughter nuclei migrate to the poles, 
where two more mitoses produce 8 nuclei (figs. 38, 42, 44). The 
