On the PithophoeacejE. 



39 



comparing the conduct of the Vaucheria-sipore and of the Pithophora-STpore 

 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 ) 2:o 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 

 Vaucheiia-spore. — From the facts now mentioned we perceive, that 

 the points of resemblance between the Pithojjhora-spore and the immove- 

 able, neutrally formed spores of two Vaucherice 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 Pithophoracece 

 and Vaucherice can 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 algae differ still more widely as to the 

 manner of their spore formation (as far as it is known) from Pitho- 

 phoracece, than the two species of Vaucherice mentioned above, it seems 

 quite superfluous to draw any special comparisons with regard to them. 

 The Pithophoracece 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 

 Cladophorece — 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 Cladophorece, as well as of Confervacece in general, 



') In V. (jeminata (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 Wittr. 1. c. 

 pag. 31 and 35). In V. liamata is, according to Walz 1. c. page 133, the time of 

 the repose of the hypnospore always very short. 



2 ) See Wittr. 1. c. t. 2, figs. 2 — 5, 7. 



