522 Black . — The Morphology of Riccia Froslii, A zest. 
Riccia Frostii. The spore contains scanty cytoplasm, but is filled with 
food material, largely in the form of oil. 
The Spermogenous Cell. 
Numerous writers have observed that all of the cells in a given segment 
of an antheridium descended from one cell divide at the same time. In 
a large antheridium many stages may be found, and particularly successive 
stages. Inasmuch as the sperms are mature about the same time, the 
divisions in different parts of the antheridium follow one another closely. 
The nuclei in all of the spermogenous cells are comparatively large, almost 
filling the cell. 
The spermatogenesis of Riccia Frostii , Aust., is difficult to follow, 
owing to the extreme smallness of the cells and their consequent blurred 
aspect when examined under high powers. A typical resting-stage similar 
to that in sporogenous cells was not observed in the cells in spermogenous 
tissue, nor was any stage found where a definite nucleolus could be distin- 
guished. The most common condition is that shown in Fig. 40. The 
chromatin, which is abundant, is grouped in the centre of the nucleus in 
a number of irregular lumps. The rest of the nucleus, which is, on the 
whole, denser than the cytoplasm, is finely granular, or may have a definite 
reticulum. It appears homogeneous, and nothing could be seen distinctly in 
nuclei at this stage, except the mass of chromatin, which stains deeply. 
The cytoplasm is uniformly granular. Two cells in early prophase are 
shown in Fig. 41. The chromatin is seen in a network of irregular lumps, 
evenly distributed in the nucleus ; in one of them (a) a central lump is 
present which resembles a nucleolus, but as the cells are small and some of 
the lumps quite large, it is possible that this body is a mass of chromatin 
which appears more globular than the others. 
In Fig. 42 the chromatin has formed a definite thread or spireme. By 
focusing, this thread could be distinguished towards the periphery of the 
nuclear membrane, and is evidently the hollow spireme stage. The next 
observed stage is seen in Fig. 43. The spireme has evidently shortened and 
thickened, then segmented. The chromosomes are collected in the centre 
of the nucleus. The cytoplasm is uniformly granular. In Fig. 44 the 
nucleus is slightly elongated, and fibres extend beyond it, resembling polar 
caps. These fibres eventually replace the nuclear membrane (Figs. 45 and 
46), and presumably are attached to the chromosomes. In Fig. 4 6 the 
separate chromosomes are distinguished a little more plainly than in Fig. 45. 
The chromosomes, which appear as round, irregular lumps, are grouped at 
the equator (Figs. 47 and 48) ; the daughter chromosomes are always 
opposite. The spindle is pointed. Frequently a broad-poled spindle is 
seen, as in Figs. 52-54. The chromosomes appear as short, curved rods, as 
seen in the polar view (Figs. 49-51), and are eight in number. An interesting 
