12 The Development of the Male Prothallium [January, 
to have divided into three cells at first, instead of two, as was 
ordinarily the case. 
Many of the prothallia show a tendency to branch quite early, 
as is shown in Figs. 9 and 10, drawn May 8th. In these the 
basal cell remains undivided, and increases but little in length, 
while the others become elongated and divided by a longitudinal 
septum, forming two parallel rows of cells that finally develop into 
the two main branches of the older prothallium. This tendency 
is more plainly seen in Figs. 11 and 12, drawn at the same time 
from specimens that had developed further. In both of these the 
rows of cells have separated at the ends so as to plainly show the 
beginnings of the branches. 
Sometimes, as in Fig. 14, there is considerable growth before 
any tendency to branching is shown; in this case the branch 
seeming to be formed by budding rather than by a division of 
the terminal cell. In contrast to this elongated form, there were 
numbers having the short thick form seen in Fig. 13. 
Observations, made May soth, showed that many of the larger 
prothallia had sent out a second root-hair from one of the lower 
celis. In some of the prothallia the branches also seemed in- 
clined to divide again, thus forming four nearly equal branches 
instead of the two ordinarily present. This was more especially 
noticed in the case of spores growing in water, probably on ac- 
count of the more nearly equal pressure on all sides, those grow- 
ing on earth being flatter and having usually but two main 
branches. At this stage the chlorophyll bodies are remarkably 
distinct, being large and bright colored. 
For some time after these observations were made, probably 
largely due to the unusually cold and dark weather, growth pro- 
ceeded quite slowly, no noticeable change being remarked for 
almost a week; by the end of this time some of the more for- 
ward prothallia had assumed a distinctly two-branched form (Fig. 
15), the branches being long and slender; from this point growth 
proceeded more rapidly, both laterally and longitudinally, the 
branches becoming flatter on account of the lateral growth of the 
cells and their division into new ones by longitudinal septa. The 
prothallia now begin to assume the irregular form that they have 
when mature, by giving off side branches at irregular intervals 
in which, as in the rapidly growing main branches, the protoplasm 
is strongly condensed at the ends (Fig. 16). ` 
