668 Lewis . — The Life History of Griffithsia Bornetiana. 
surrounded by a mass of food material, which is probably derived from the 
stalk-cell. The other nuclei at the same time lie in clear cytoplasm in 
which little stored food is visible (Fig. 127). 
During the progress of these changes in the nuclear content of the 
tetrasporangium, the deeply staining granules in the cytoplasm disappear, 
so that by the end of the first mitosis they are no longer visible. At the 
same time, the large vacuoles in the cytoplasm give place to smaller, more 
regular ones. 
Cleavage of the cytoplasm begins always when the four nuclei begin to 
move toward the centre of the tetrasporangium. which happens soon after 
their formation. The hautschicht folds inwards along planes which, if 
continued to the centre of the cell, would cut the protoplast into four equal 
parts, presenting the familiar tripartite arrangement (Fig. 128). However, 
the partitions are produced inwards only about two-thirds of the distance 
to the centre of the cell (Pl. LIII, Fig. 129). The central portion of the 
tetrasporangium is occupied by the four definitive spore nuclei with their 
envelopes of kinoplasm which are in contact with one another, so that a 
rather definite nucleo-kinoplasmic mass is formed. In the very centre of 
the tetrasporangium lies the portion of the undifferentiated cytoplasm 
enclosed by the nucleo-kinoplasmic mass (Fig. 130). 
The nuclei at this stage are either spherical or somewhat biscuit-shaped, 
the inner surface being less convex than the outer. The nucleolus has by 
this time fragmented into 12-14 granules, similar in appearance to those in 
the nucleolus of the tetraspore-mother-cell before synapsis. 
At this point of development 5-10 per cent, of the tetrasporangia begin 
to show degenerative changes and do not develop further. The outer 
surface of the tetrasporangium becomes wrinkled, and the nuclei become 
very much flattened, almost wafer-like. The entire contents of the proto- 
plast stain very heavily, owing to the presence in the cytoplasm and in the 
nuclei of numerous dark granules. These degenerating tetrasporangia are 
easily distinguishable, even in the living condition, by reason of their dark, 
opaque appearance, and some are to be found in every tetrasporangial 
sorus. What causes lead to their degeneration I have not been able to 
determine. 
In the normal tetrasporangia, the cleavage partitions, which represent 
folds of the hautschicht , but which appear in section as a single line except 
near the periphery (Fig. 129), split so as to reveal clearly their double 
nature. At the same time the cytoplasm, which lay in close contact with 
the partitions, separates along the line of the partitions so that the cleavage 
furrows become wide as well as deep (Fig. 130). Even at this stage, 
however, they extend no further in than to the edge of the nucleo- 
kinoplasmic mass. Coincident with these changes in the partitions, the 
nuclei which were flattened become again approximately spherical. 
