38 Veit Brecher Wittrock. 



ought to be placed nearest to Pithophovaccœ in regard to the reproductive 

 system. Looking, to begin with, for a form of phmts which would show 

 a formation of spores reminding us of that of the Pitho2)lioracecL', we 

 find a form of this description only in one group of plants, that of the 

 Vaucheriaceœ ; and, within this group, only in two species, Vmiclicria 

 geminata (Vauch.) Walz, and ]". hamaia (Vauch.) Walz. Only in 

 these (as far as wo know) have been found immoveable spores, formed 

 neutrally (at least part of the other species have, we know, neutrally 

 formed moving spores, so-called zoospores). The formation of spores 

 in both these species ') takes place in a manner which calls to mind, 

 in some of its phases, that of the rithoplioraeeœ. Here, as Avell as in 

 Pithrplioracea'^ the proceeding is introduced by a slight widening of that 

 part of the cell in which the spore is to be formed; here, as in Pitho- 

 phoraceœ^ a quantity of the chlorophyll-coloured protoplasm passes into 

 the widened part, and here also the part of the cell thus filled with 

 chlorophyll is separated from the other part by a transversal cell-wall 

 formed succedaneously. So far the resemblance goes. We will now 

 observe the differences. These are: l:o and essentialh', that the cell 

 rich in chloroph3dl and formed in the manner now described does not 

 grow into a spore in Vaucheriœ^ although it does in Pithophoraceœ^ but 

 in Vaucherice it grows into a mother cell of a spore, formed within it 

 through cell-rejuvenescence; 2:o and as a consequence of the preceding, 

 that the spore in Vaucherice does not (as in Pitltophoracece) make use of 

 the membrane of the mother cell, but forms one for itself; 3:o that the 

 spore does not (as in Pitliophoracece) remain for a long time united to 

 its mother specimen, but is made free ver}^ soon by the dissolution 

 of the environing wall of the mother cell (in analogy with the 

 emission of the zoospores from their mother cells iu other Vauche- 

 riw); 4:o that the spore is always formed terminally in Vaucheriœ, in 

 contradistinction from what is the case in Pitlioplioraceœ ; and 5:o that 

 no subsporal cells devoid of chlorophyll occur in Vaucherice^ as is the 

 case in Pithophoracece^ because the vegetative system consists in Vaucherice 

 of only one cell (but that a gigantic one), whicii commonly does, far 

 from being exhausted by one act of spore formation, beget numerous 

 spores and sometimes a more or less considerable number of oogonia 

 and antheridia besides. ^) If we now continue our investigations by 



') Coinpavf WiTTii. Utvcckl. af Vmich. pag. 34 and 35; and Walz Boitr. z. 

 ]\lürpli. d. Vauch. pag. 132 and 133. 



-) See Witte. 1. c. plate 2, fig. 7. 



