Fertilization of the F loridee. 3 
body*. Sometimes in this case the main branch of a system 
of ramification projects particularly in the midst of its nume- 
rous lateral branches (Batrachospermum) ; sometimes, by rapid 
growth of the lateral branches which arrange themselves be- 
side it in equal development and strength, it becomes con- 
cealed and unrecognizable. 
The individual filaments increase in length by apical growth 
with acropetally advancing division of the terminal cell, which 
sometimes exceeds the rest in size, and is then easily distin- 
guished as the apical cell, and sometimes does not differ from 
the other cells. Hence the individual branches of the thallus 
are sometimes seen to be provided with a distinct apical cell 
at the apex of the main branch of the whole system of ramifi- 
cations, and sometimes, if neither the main shoot of the system 
of ramifications nor the terminal cells of the individual branches 
stand out distinctly, they grow in length apparently with an 
apical surface, while in all cases the same mode of apical 
growth takes place. 
The apical growth of the cellular filament is generally fol- 
lowed by a frequently very abundant intercalary growth by 
extension of the individual cells. In this case, however, no 
(orthogonal or oblique) transverse division of the individual 
joint-cells ever takes place, any more than a longitudinal 
division, with a divisional wall occupying the organic longi- 
tudinal axis of the cellf. ‘The only divisions which break 
* From this dissimilar structure of the thallus the differences in habit 
of the different forms of thallus appear much greater than the differences 
of the general mode of growth really are. These essentially consist in a 
different behaviour of the older lamelle of the mother-cell membranes. 
Thus if these older lamella of the mother-cell membranes are perforated 
locally during the outgrowth of a branch-cell, the branch-cell grows 
into a free filamentous branch. On the other hand, if these lamelle are 
only stretched and lifted up by the growing branch-cell, the branch-cell 
remains united with the neighbouring cells in a more or less closely packed 
so-called parenchymatous cell-union, and held together by a common ex- 
ternal membrane. If these common cell-membranes then swell up gela- 
tinously the thallus assumes the form of a system of branched cellular 
filaments, which are enclosed and enveloped by a more or less dense 
jelly. 
: This heterogeneous development of the thallus consequently never pre- 
cludes a near relationship of two Floridean genera, however different they 
may be in habit at the first glance. 
For the same reason, however, a near relationship of two genera can- 
not any more be excluded because the spore-forming mass of tissue, the 
so-called nucleus of the cystocarp, forms, in the one case, a closed cellu- 
lar body, and in the other a branching tuft of filaments (compare, for 
example, Helminthora and Nemalion, Callithamnvon and Setrospora, 
Cruoria and Cruoriopsis, Chylocladia and Lomentaria, c.). ; 
+ For the establishment of this fact, in many cases, very wearisome 
and troublesome investigations are necessary, So that it res easily be 
