On THE PITHOPHORACES. 35 
V. ON THE AFFINITIES OF PITHOPHORACEH AND THE PLACE OF 
THIS ORDER 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 
Pithophoracee. Already the circumstance that the forms now found to 
belong to the new order of Pithophoracee, 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 Pithophoracee and Cladophoree 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 
Cladophoree organs even occur which are of the same nature as the 
helicoids of Pithophoracee.*) The resemblance as to the cauloid part 
1) Only one author, Grunow, has had a conception, that one of the forms 
commonly referred to the genus of Cladophora ought perhaps to be aggregated to a 
genus-type separate from Cladophora. ‘This author says in »Reise 8. M. Freg. 
Novaray pag. 39 of Cladophora fRocttleri (Roth) Kiitz. (= Péthophora Roetileri 
nob.): »VYon Rorn als Ceramiwm beschrieben, verdient diese Art vielleicht einmal 
bei genauerer Kenntniss der Cladophora-arten 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 Cladophora thus: In einigen Fallen beobachtete 
ich (in a brasilian form) Faden mit spatelf6rmig angeschwollenen Astenden mit ge- 
hauften Chlorophyll-Inhalt, aus denen sich durch Abschniirung die Fruchtzellen zu 
entwickeln scheinen.» 
7) Compare v. Mohl, Verm. d. Pflanzenz., pages 363 and 366, pl. 13 (on 
Cladophora glomerata). 
3) J. M. Lorentz represents in Die Straton. v. Avgagr. on pl. 4, figs. 14 and 
15 parts of the thallus of Mgagropila Sauteri, where two of the terminal cauloid 
cells have assumed, by the formation of small processes at their top, almost the same 
forms as those common in the helicoids of P. Cleveana nob. As these top cells also 
serve the same purposes as the organs of Pithophoracee, | do not hesitate to regard 
them as real helicoids. They are, like the helicoids of Pithophora, very rich in chloro- 
phyll, but not only in their upper and ramified part, but also in the lower. In 
Kirzinc, Tab. Phyc., Band 4, pl. 66 a representation is given of Avgagropila her- 
