Graham . — Nuclear Division of Preissia commutata . 671 
differentiated into spore mother-cells and elaters. All the sporogonia are 
not in the same stage of development, though they are all near the same 
stage. 
When the differentiation in the sporogonia takes place, the spore 
mother-cells are embedded in a gelatinous substance. There are plastids 
in all the cells in the sporogonia and those in the elaters develop chlorophyll. 
There is also chlorophyll in the wall of the sporogonium. When the wall 
of a sporogonium is cut and its contents are forced out on a slide the chloro- 
phyll bodies in the elaters are conspicuous. The gelatinous substance in 
which the spore mother-cells and elaters are embedded is colourless, viscid, 
and holds the contents of the sporogonium together on the slide. 
In preparation for fixing, the sporogonia were separated from the 
gametophore and the pseudoperianth was cut away before they were placed 
in the killing fluid. Hermann’s fluid, Carnoy’s fluid, and Juel’s fluid 
were used. Material killed in Hermann’s fluid was best. Through 
experience during the two preceding springs, it was found that any killing 
solution containing chromic acid tended to harden the mucilaginous sub- 
stance in which the spore mother-cells are embedded, and the cells were 
plasmolysed. Sections were cut 4, 5, 6, 7, and 9 [x. They were stained with 
Flemming’s triple stain, Heidenhain’s iron-alum-haematoxylin, and the 
Flemming’s triple stain, substituting pyoktanin for gentian violet. 
The spore mother-cell in the resting condition is broadly elliptical. 
The cytoplasm presents a coarse open or foamy appearance. It has the 
same appearance in the living condition. Lying in the cytoplasm between 
the nucleus and the cell wall are groups of plastids. In the centre of the 
cell there is a spherical nucleus. The reticulum in the resting nucleus is 
made up of a number of fine anastomosing threads. The chromatin bodies 
are small, very numerous, and are situated at the angles of the reticulum 
(Fig. 1). One or more vacuoles appear in the reticulum at this stage. 
There may be as many as four large nucleoli in the nucleus of the spore 
mother-cell. 
The spherical nucleus of the resting cell enlarges. The fine reticulum 
changes into a coarse network of threads (Fig. 2). Some of the threads 
making up the network can be traced for some distance, and it is evident 
that at this early prophase a long slender thread is being formed. Near 
the nucleoli in the section represented by Fig. 2 are fine linin threads. The 
reticulum is of unequal thickness at this phase ; the strands near the nucleoli 
remain in the condition of the linin of the resting nucleus the longest time. 
The chromatin at this early prophase is more conspicuous than in the 
resting nucleus, the individual bodies having increased in size. Here, as in 
the nucleus of the resting cell, the chromatin bodies lie at the angles of the 
reticulum. 
The growth of the nucleus continues. The condition of the reticulum 
