410 BOTANICAL GAZETTE [DECEMBER 
so that sperm mother cells are developed directly from the axial 
siphon of the antheridium. 
The cytoplasm of the sperm mother cell (fig. 62) has a very delicate 
granular structure and is generally destitute of plastids. The nucleus 
in the resting state contains a fine network and a nucleolus. Pro- 
chromosomes, 20 in number, are formed in the network (jigs. 63, 634) 
and are connected by weakly staining linin threads. The prochromo- 
somes increase in size and become rod-shaped chromosomes (jigs. 
64, 64a). : 
Kinoplasm becomes differentiated from the surrounding cyto- 
plasm and accumulates at the poles of the elongating nucleus, and a 
centrosome-like body appears at each pole (figs. 64, 64a). The 
stage of prophase passes into metaphase (jigs. 65, 65a), when centro- 
sphere-like structures are well-developed and the axis of the spindle 
is shorter than the diameter of the equatorial plate, as is the case 
during the mitoses within the carpospores, tetraspores, and vegetative 
cells. The number of chromosomes is clearly 20 in this mitosis, as 
shown in polar view of the equatorial plate (fig. 66). The nuclear 
membrane is present during metaphase (fig. 67), and as the two 
groups of daughter chromosomes separate a vacuole intrudes between 
them (figs. 68, 69, 70). The centrosphere-like structures are not 
recognizable after metaphase. The set of daughter chromosomes 
which passes to the basal region of the cell becomes aggregated, 
surrounded by a nuclear membrane, and enters into a resting condi- 
tion; while the chromosomes of the other set, passing to the upper 
part of the cell still retain their individuality, although it is probable 
that a very delicate membrane may be formed (fig. 70). 
A cleavage furrow in the middle region of the cells appears (fig. 72)s 
and by the same mechanism as in the case of vegetative cells effects 
a separation of the upper half as a sperm cell from the lower half. 
The greater part of the large vacuole is included in the sperm, which 
consequently has a relatively small amount of protoplasm in com- 
parison with its size (figs. 72, 73). The cleavage furrow which cuts off 
the sperm cell crosses the sperm mother cell obliquely, and conse- 
quently the sperm assumes a lateral position, allowing the sperm 
mother cell to elongate. When the matured sperm is detached esse 
pletely from the sperm mother cell, the latter has assumed again Its 
characteristic extended form (fig. 75). 
