44 



Veit Beecher Wittrock. 



parag. 1, pages 6 and 7). The relative position of the branches also 

 gives specific characters thus, that the branches are in some species 

 regularly placed singly, in others two and two opposite to each other, 

 and in others three or four in a whorl, partly at least (see above pages 

 6 and 7). The existence or non-existence of so-called subsporal branches 

 may also be used as a specific character. *) The same may be said of 

 the helicoid cells; in one species, P. Cleveana nob., they are found in 

 great quantity, in the others only very sparingly. That specific char- 

 acters may be had also from the nature of the rhizoid, when a more 

 complete knowledge of it is obtained, I think not improbable, although 

 this part of the thallus, being in general rather rudimentary, seems to 

 have a greater tendency to vary than the cauloid. 



The characters most essential in the distinguishing of species 

 (and particularly of groups of species) are obtained from the reproduc- 

 tive system. In part of the species, viz. P. cequalis nob., P. oedogonia 

 (Mont.) nob., P. Cleveana nob., P. kewensis nob. and P. sumatrana 

 (v. Mart.) nob. (that is, the american forms, the european one, and 

 one of the asiatic), all the spores are (in each species) of the same 

 principal shape, though differing as to length and thickness;' thus, that 

 the inclosed spores are all either cask-shaped or cylindrical, and the 

 terminal are all either cask-shaped or cylindrical with the top pointed 

 like a cone. But in the other species, viz. P. polymorplxa nob., P. Zelleri 

 (v. Mart.) nob. and P. Eoettleri (Roth) nob. (all asiatic species) we find 

 two or more forms, at least of inclosed spores. In P. polymorpha nob. for 

 instance they are of three kinds, viz. some cylindrical, some cask-shaped 

 and some of an irregular shape; whilst the terminal spores are of two 

 kinds, viz. some cylindrical and some cask-shaped, in both cases with 

 the top obtusely pointed and somewhat rounded. In P. Eoettleri (Roth) 

 nob. the case is analogous to that in P. polymorpha nob. In P. Zelleri 

 (v. Mart.) nob. the inclosed spores are of three kinds, but the terminal 

 are all alike. — It is on this peculiarity as to the spores, viz. that 

 they are in some species of the same principal form, but show in the 

 others different forms , that I have founded the two subdivisions, 

 Pithophorce isosporece and Pitlioplioras heterosporece, in which the genus is 

 divided. 



*) Besides in P. Zelleri (v. Mart.) nob. subsporal branches are also found at 

 least in most specimens of F. oedogonia (Mont.) nob. (see pi. 6, figs. 4 and 5). 



