On THE PITHOPHORACES. 29 
species of Pithophora, spores which support branches (pl. 1, fig. 13, 16, 
18 sp; pl. 2, fig. 2. 3, 18, 15 sp, and others) "); but this does not de- 
pend on a ramification from the spore cell, but on the fact, that the 
original common mother cell of the branch and of the spore has first 
formed a-~branch by cell-prolification (= Abschniirung in the German 
language) and afterwards, by the usual division into two, a spore in its upper 
end G. e. in that part of the cell, which supports the branch just for- 
med). As exceptions, branches may be formed even from the subsporal 
cells which are, as a rule, branchless. This is not seldom the case in 
P. Zelleri (v. Mart.) nob. The vegetative cells are richer in protoplasm 
in this species than in the others. The consequence of this is, in 
general, that each cell, at least in the principal filament, forms not only 
one, but as much as two spores. But sometimes the cells of the prin- 
cipal filament form but one spore each, and then the not mconsiderable 
quantity of protoplasm still remaining in the original mother cell is used 
to form a normal branch, instead of a spore (pl. 1, fig. 9 bs). In the 
other species of Pithophora I have observed a subsporal cell carrying 
a branch-only in one case, to wit in the specimen of P. kewensis 
nob. which I have represented pl. 2, fig. 7 (the subsporal branch is 
marked bs). 
As we have seen by the exposition given above, a cauloid and a 
rhizoid cell are formed simultaneously, in the germination of the spore. 
But, whilst the first cauloid cell gives origin by and by, by a continued 
and in various ways modified division into two, to a great quantity of cells, 
which form together a cauloid of a comparatively complicated structure, 
no further development takes place, as a rule, in the first rhizoid cell. 
A natural consequence of this is, that the rhizoid part of the thallus 
has a very simple structure; it is unicellular. Now and then it happens, 
however, particularly in P. kewensis nob., that the rhizoid does not 
remain in this low stage of development. In this case, the first rhizoid 
cell increases and divides into two in the same manner as the first cauloid 
cell, with the difference only, that the increase in the rhizoid always 
takes place in a different direction from that of the cauloid. By this 
increase the rhizoid grows bicellular instead of unicellular (pl. 4, 
fig. 11. Obs. A formation of spores, which has taken place later, has 
*) Only in P. @qualis nob. I have never found branches supported by spores. 
Even the cells of the principal filament seem here to lack the power of producing 
more than one of these, a branch, or a spore (pl. 1, fig. 4, 5). 
EEE 
