On THE PITHOPHORACES. 47 
the order would embrace only tropical (and subtropical) forms. At all 
events it has the centre of its geographical distribution between the 
- tropics, and in this respect stands alone among the orders of freshwater 
algze as yet known. 
If we inquire in which parts of the world the different species of 
Pithophoracee are met with, we find that four, viz. P. swmatrana (v. Mart.) 
nob., P. polymorpha nob., P. Roettleri (Roth) nob. and P. Zelleri (v. 
Mart.) nob. are found in Asia; that three, viz. P. equalis nob., P. oedo- 
gona (Mont.) nob. and P. Cleveana nob. are found m America; and 
one, viz. P. kewensis nob., in Kurope.*) Even in Australia a Pithophora 
is found, the one mentioned before as existent in the Grunowian collec- 
tion, gathered in the isles of Samoa. From Africa alone no Pithophoracew 
are as yet known; but that they exist there is more than probable, 
because everything we know of their distribution seems to indicate that 
they are common in the freshwater pools of the tropical countries. — 
As to a more particular account of the localities of the Pithophoracea 
as yet known, I may refer to the descriptions of the different species 
given hereafter. 
VIII. DESCRIPTION OF THE SPECIES. 
Before giving a description as complete as possible of the spe- 
cies of Pithophoracee known to me, I will here try to give a diagnosis 
of the order. 
ORDER PITHOPHORACEA nob. 
Chlorophylliferous cladophora-like freshwater alge, con- 
sisting of cells, formed by bipartition of the terminal cell. 
The thallus having two distinct parts, viz. l:o the cauloid part, 
developed from the germinated spore upwards, propagative 
and almost always branched; the branches placed a little 
space below the top of their supporting cells; 2:0 the (mor- 
1) As to the country where P. kewensis nob. is indigenous, it seems 
probable that it is the tropical part of America. Here both the species occur, 
which show the nearest relationship to P. kewensis nob., viz. P. oedogonia (Mont.) 
nob. and P. Cleveana nob. 
) 
