674 Lewis . — The Life History of Griffithsia Bornetiana. 
Opportunity has not occurred for the examination of a large series of 
dividing nuclei in the sporelings, but in the cases examined the mitoses were 
of the type usual in vegetative nuclei. In the dividing nuclei of sporelings 
from tetraspores, about six or seven chromosomes appear on the equatorial 
plate (Fig. 143). In the sporelings from carpospores the number of 
chromosomes is always greater than this, but appears to be less than 
the number that might be expected (14). There is believed, however, 
to be sufficient evidence for regarding these nuclei as diploid in character. 
The daughter-nuclei withdraw to opposite sides of the sporeling 
(Fig. 1 41) and divide again to form four nuclei, which in turn divide 
to form eight (Fig. 142), then sixteen (Fig. 343). The increase in the 
number of nuclei is not accompanied by a corresponding increase in the 
size of the spore ; the size of the nuclei becomes less with each succeeding 
division. At about this time, the sporeling changes its shape, pushing out, 
at the point of attachment, a small rounded projection, which later becomes 
cut off as the basal cell. Immediately after this projection is formed the 
sporeling elongates, becoming about twice as long as broad, but without 
undergoing cell-division (Fig. 144). 
As these changes take place the cytoplasm migrates more and more 
to the periphery. The central part of the sporeling is occupied by small 
regular vacuoles, whose exceedingly thin walls are roughly hexagonal 
in section (Fig. 141). A single large central vacuole such as is character- 
istic of the vegetative cells of the older plants is not usually formed until 
the sporeling reaches the 3-celled stage. 
Cell-division occurs usually when about sixteen nuclei are present. 
A wall at right angles to the long axis of the sporeling cuts off a basal from 
an apical cell (Fig. 145). Shortly after this, without further elongation 
of the sporeling, the apical cell divides into two by a wall parallel with the 
first (Fig. 146). The details of the formation of these walls were not 
followed out. As the partitions have not been seen to assume the arched 
shape characteristic of the first type of cell-division at other points in 
the life-history (see p. 649), it may be inferred that they are formed by the 
ingrowth of a ring of cellulose (p. 650), such as is formed in the divisions of 
the cells of Cladophora. From the two divisions a small obovate 3-celled 
sporeling results, which consists of a smaller, somewhat pointed basal cell 
and two larger rounded cells towards the apex, the three cells lying 
in a row (Fig. 147). At this stage, the chromatophores and protoplasm 
are so closely packed in the peripheral portion of the cytoplasm that 
the sporeling appears dense and opaque. The pointed end of the basal 
cell is filled only with homogeneous protoplasm, starch-grains, and chro- 
matophores being absent from this region. Intercellular connexions were 
not demonstrated in the small 3-celled sporelings, though they are apparent 
after the enlargement of the cells. 
