Lewis . — The Life History of Griffithsia Bornetiana. 663 
seems probable that this material is passed up into the cystocarp from the 
cell below. 
Asexual Reproduction (Tetraspores). 
The tetraspores are formed in a ring around the upper border of any 
cell below the apex of the filament (Fig. 4). The ring of tetraspores 
appears to encircle the node, fitting snugly in the constriction between 
neighbouring vegetative cells. On the outside of the tetraspores a circle of 
involucral rays grows up around the sorus. The number of these is 
variable ; there are often only six or eight ; sometimes there are as many as 
twenty. They appear rather late in the development of the sorus, in some cases 
the most advanced tetraspores having already matured before the involucral 
rays are formed. The rays are expanded curved plates, connected at the 
base with the vegetative cell, and free laterally and terminally. Usually 
neighbouring rays are in contact at the sides, so that the circle of tetraspores 
is well screened from without. Each ray is a single cell similar in 
appearance and in structure to the outer cell of the involucral ray of the 
cystocarp. Where the rays are in connexion with the vegetative cell, the 
plugs characteristic of the intercellular connexions elsewhere are formed. 
The tetraspores are formed as follows : — Around the upper border of a 
young cell below the apex, protoplasm accumulates in small rounded 
masses, each containing a single nucleus (Fig. 98). The cell-wall near each 
protoplasmic accumulation becomes gelatinous, which allows the accumula- 
tions to protrude as small papillae (Fig. 99). Each of these papillae 
early becomes cut off from the mother-cell by a delicate dome-shaped 
membrane (Fig. 100). The cell so formed, with its nucleus, increases in 
size, and at the same time the membrane loses its convex form and becomes 
flattened (Fig. 101). 
The formation of these primary tetrasporic cells seems to take place 
entirely independent of nuclear division. 
On the upper border of each of these cells a finger-like outgrowth of 
cytoplasm is protruded (Fig. 102). The nucleus then divides by mitosis in 
the way described for vegetative nuclei of the tetrasporic plant (Fig. 103). 
One of the daughter-nuclei remains in the basal portion of the cell, the other 
passes into the cytoplasmic outgrowth, a membrane appearing between the 
nuclei (Fig. 104). Thus is formed a small two-celled branch, with a single 
nucleus in each cell (Fig. 105). The lower may be called the stalk-cell, 
while the upper is the tetrasporangium or tetraspore-mother-cell. 
During the growth of this structure, the stalk-cell pushes out another 
cytoplasmic projection similar to the one first formed. The nucleus divides 
by mitosis (Fig. 106), one of the daughter-nuclei remaining in the stalk- 
cell, and the other passing into the projection, which becomes cut off like 
the first. Thus a second tetraspore-mother-cell is formed on the stalk-cell. 
