672 Lewis . — The Life History of Griffithsia Bornetianci. 
been seen in only a single nucleus of the portion of the plant bearing the 
tetraspore-like structures. In this case, in the dividing nucleus of the 
stalk-cell, the number of chromosomes was seen to be seven (see Fig. 135). 
The branches bearing tetraspore-like structures are of the same type as 
those of the normal tetrasporic plant, but are composed of cells that are on 
an average a good deal smaller. 
The early development of the tetraspore-like structures is similar 
in every detail to corresponding stages in the development of the normal 
tetraspores. Small uninucleate papillae are cut off from the upper border 
of the vegetative cells. Each divides to form a short two-celled branch, 
the lower cell representing the stalk-cell of the tetrasporangium, the upper 
corresponding to the tetraspore-mother-cell (Figs. 134, 135). The stalk-cell 
increases in size and becomes vacuolate, the mother-cell also becomes 
larger, but remains somewhat smaller than the normal tetraspore-mother- 
cell. The average diameter of the fully formed mature mother-cell is about 
20-22 // as against 24 // for the mother-cell of the tetraspore. The nucleus 
in the two cases shows the same configuration, but remains smaller in the 
mother-cells borne on the sexual plant (Fig. 135). Nuclear material 
passes out into the cytoplasm, where it forms small darkly staining 
granules. 
Involucral rays are formed in the ways characteristic of the tetraspore- 
sorus, usually as outgrowths from the vegetative cell outside the ring 
of spore-mother-cells, exceptionally as lateral outgrowths from the stalk-cell 
(Fig. 136). 
The further development of the mother-cells on the sexual plant differs 
strikingly from that of the normal tetraspore-mother-cells. In the majority 
of cases the nucleus divides (whether by mitosis or amitosis I have not yet 
been able to determine), and cleavage begins at the periphery (Fig. 137). 
The cleavage furrows do not advance far into the body of the mother-cell. 
The surface of the cell begins to show irregular wrinkling, and degenerative 
changes set in similar to those described for certain tetraspore-mother-cells. 
The number of nuclei in cells in which cleavage furrows begin is usually 
4-8, of which some are very much larger than the rest (Fig. 137). 
One case deserves special mention. Sixteen nuclei lie scattered in the 
cell which shows no trace of the formation of cleavage furrows (Fig. 138). 
The whole cell presents the appearance of a germinating spore. It would 
seem that here the cell corresponding to the tetraspore-mother-cell behaves 
as a monospore, though whether such a cell ever produces a normal plant 
is uncertain. 
The chromosome-history of the nuclei of the cells just described has 
not yet been determined. 
