On the Pithophoeace^. 35 



V. ON THE AFFINITIES OF PITHOPHOEACEJ] AND THE PLACE OF 

 THIS OEDER IN THE SYSTEM. 



If we regard, at first, only the vegetative system, we easily find 

 a group of plants which in this respect shows a very close affinity to 

 Pithoplwraceœ. Already tlie circumstance that the forms now found to 

 belong to the new order of Pithophoraceœ^ which have formerly been 

 described in floristic works, have all been described as species of the genus 

 Cladophora^ ') gives an unmistakeable hint on this head. The resemblance 

 between Pithojjhoracece and Cladophoreœ as to the vegetative system is, 

 in fact, very great. In both, the thallus consists of cylindrical chloro- 

 phylliferous cells, connected so as to form a ramified series of cells; in 

 both, the formation and increase of the cells, as well as of the series 

 of cells, takes place essentially in the same manner; in both, the deve- 

 lopment of branches follows in general the same law; ^) and in some 

 Cladophoreœ organs even occur which are of the same nature as the 

 helicoïds of Pithophoraceœ. ^) The resemblance as to the cauloïd part 



') Only one author, Grunow, has had a conception, that one of the forms 

 commonly referred to the genus of CJadophora ought perhaps to be aggregated to a 

 genus-tvpe separate from Cladoplwra. This author says in »Reise S. M. Freg. 

 Novara» pag. 39 of Cladoj^liora Eodtlcri (Pioth) Kütz. {= Fülwpliora EocUlcri 

 nob.): »Von EoTH als Ceramiiini beschrieben, verdient diese Art vielleicht einmal 

 bei genauerer Kenntniss der Cladoijhora-urten als eigene Gattung davon abgeschieden 

 zu werden». In the same place he also pronounces his opinion on the probable origin 

 of the spores (»Fruchtzellen») of this Cladoplwra thus:» In einigen Fällen beobachtete 

 ich (in a brasilian form) Fäden mit spatellormig angeschwollenen Astenden mit ge- 

 häuften Chlorophyll-Inhalt, aus denen sich durch Abschnürung die Fruchtzelleu zu 

 entwickeln scheinen.» 



-) Compare v. Mohl, Verm. d. Pflanzenz., pages 363 and 3(36, pl. 13 (on 

 Œadophora (ßomerata). 



^) J. M. LoRENTZ represents in Die Straton. v. JEgngr. on pl. 4, figs. 14 and 

 15 parts of the thallus of ^(jagropila Saiitcr/, where two of the terminal cauloïd 

 cells have assumed, by the formation of small processes at their top, almost the same 

 forms as those common in the helicoïds of P. Cleveana nob. As these top cells also 

 serve the same purposes as the organs of Pithoplwraceœ, I do not hesitate to regard 

 them as real helicoïds. They are, like the helicoïds of Pithopliora, very rich in chloro- 

 phyll, but not only in their upper and ramified part, but also in the lower. In 

 KüTziNG, Tab. Phyc, Band 4, pl. 66 a representation is given of jEgagropila her- 



