On THE PITHOPHORACEA. 39 
comparing the conduct of the Vaucheria-spore and of the Pithophora-spore 
in germinating, we first find a. resemblance in the fact of their both 
reposing for a time before the germination commences, *) and farther 
one more in their forming the new plant immediately by the stretching 
of their membrane to form cylindrical processes. The differences, on 
the other side, are: l:o that, whilst the Pithophora-spore, in germinating, 
regularly sends forth two diametrically opposed processes, the Vaucheria- 
spore is very irregular in this respect, sometimes sending forth two 
processes, sometimes three, and sometimes only one; *) 2:0 and essentially, 
that whereas a parting wall, dividing the Pithophora-spore into two cells, 
regularly appears, no such cell-wall is ever formed in the germinating 
Vaucheria-spore. — From the facts now mentioned we perceive, that 
the points of resemblance between the Pithophora-spore and the immove- 
able, neutrally formed spores of two Vaucheriw are, it is true, not 
few, but that the differences are at the same time so numerous and of 
so great importance that a nearer relationship between Pithophoracew 
and Vaucherie ean from the nature of the spores not be supposed to 
exist. That the vegetative system in the two groups still less gives 
cause to a supposition of this kind, is so evident as to need no further 
elucidation. 
As all other groups of alge differ still more widely as to the 
manner of their spore formation (as far as it is known) from Pitho- 
phoracee, than the two species of Vaucherie mentioned above, it seems 
quite superfluous to draw any special comparisons with regard to them. 
The Pithophoracee would thus seem to have an extremely isolated po- : 
sition as to the spore formation. But that connecting points may be 
found, even in this respect, between them and another group — the 
Cladophoree — I have already indicated, and I will now endeavour to 
make this still clearer. 
It is well known that the essential and characteristic reproductive 
organs of the real Cladophorew, as well as of Confervacee in general, 
1) In V. geminata (Vauch.) Walz the duration of the repose of the neutrally 
formed spore varies considerably. The spores formed towards the end of the autumn 
repose during the whole winter (here, in Sweden, several months) before germinating. 
But the spores which are formed in spring repose for a very much shorter time, at 
most a week and most frequently only two or three days (see further Wirrr. l. c. 
pag. 31 and 35). In V. hamata is, according to Wauz 1. c. page 133, the time of 
the repose of the hypnospore always very short. 
2) See Wirtr. |. c. t. 2, figs. 2—5, 7. 
