26 Veit Brecuer Wirrrock. 
in half-fertile-half-sterile specimens, the formation of spores is begun 
already before the ramification is completed (pl. 2, fig. 5, 7). It then 
not seldom happens, especially in P. Cleveana nob., that the formation 
of a branch being commenced in a cell, it is interrupted by the for- 
mation of a spore in the same cell. A cell of this description then 
seems to have, as it were, suddenly changed its plan, ceasing the for- 
mation of the branch in order to form in its place a spore. Spores 
formed during those circumstances are recognized by carrying on one 
of. their sides a greater or smaller process, often resembling the beak 
of a bird (pl. 2, fig. 3, 14, 15 sr; pl. 3, fig. 8 sr). That the formation 
of branches and spores may take place at the same time is also shown 
by pl. 8, fig. 5. Here we find a branch process, formed so lately as 
not yet to be parted by a cell-wall from its mother cell, but of which 
the upper part, st, is already in the act of transforming itself into a 
spore.!) This circumstance is still more evident in such rather rare 
and very short branches, as are wholly transformed into spores, so called 
sessile spores. I have found those mostly in P. Cleveana nob., but 
also in P. kewensis nob. (pl. 2, fig. 2 ss) and P. polymorpha nob. (pl. 
ings Wess): | 
As we have found from the exposition given above, the increase 
in length of the series of cells 1s produced by the activity of the top 
cells; while the formation of branches is effectuated by the inclosed 
cells. Here the followmg remarks may be made. Bipartition of the 
cells inclosed in the series occurs now and then. Thus, the cells marked 
p and 6 in pl. 3, fig. 1 are daughter cells of an inclosed cell. Neither 
is the formation of branches from top cells without an instance. Fertile 
specimens of small size of P. Cleveana nob. are not unfrequently found 
with not only one, but even two branches developed from the terminal 
cell of the principal filament, which has then also developed a spore in 
its top (pl. 2, fig. 13; pl. 4, fig. 16). Of P. polymorpha nob. I have found 
one specimen, the one represented pl. 1, fig. 17, where two terminal 
cells, one belonging to the principal filament, the other to a branch, 
show a beginning ramification (both the branchlets will here consist of 
1) In the further process of the development a parting wall will be formed 
here first at ba’, and afterwards, when the whole chlorophyllaceous mass of the branch 
cell has passed into the widened part of the cell, at ba’. All this being done, the 
original mother cell will form a spore in its top. Compare pl. 2, fig. 3 st, and pl. 
5, fig. 4 sé. 
