FRESHWATER ALGJE 273 



every sign of being subjected to very rigorous conditions. The small amount of 

 growth from one of the old cells of a preceding season could be well seen in most of 

 the specimens. (Vide PL XXIV, Figs. 12-14) 



Among the filaments in the H or midium- stage, which formed a felty covering over 

 the ground near Blue Lake on December 11, 1908, were all the early stages of develop- 

 ment which so much resemble both small and large colonies of Pleurococcus. They 

 have, however, several distinguishing features,- one of which is in the form and 

 disposition of the chloroplast. 



The expanded thalli were abundant from several places near Cape Royds and 

 from 5j miles south of Cape Irizar, South Victoria Land. All stages in the.develop- 

 ment were frequent, and were very similar to those figured by Wille (in Nyt Mag /. 

 Naturvidenskab, Bd. 40, Heft III, 1902, t. 3) from another Antarctic region. The 

 spacing of the cells was exactly as in P. crispa. (PL XXIV, Figs. 8, 9) 



It would appear that the great mass of the Antarctic Prasiola differs in no way 

 from the northern P. crispa. The fully expanded and plicate thalli attained a breadth 

 of 13 mm., the cells varying from 6 to 9 M in diameter. 



Var. aspera var. n. (PL XXIV, Figs. 15-18) 



Filis in statu Hormidio modo visis ; membrana exteriori cellularum incrassata et 

 lamellosa, marginibus valde et irregulariter asperis ; cellulis ssepe brevissimis. 



Crass, fil. 12-18 /x; diam. cell. 9-11 /*; long. cell. 1.4-7.5 p. 



Hob. In small pond, Cape Royds. 



This peculiarly rough variety certainly does not agree with the published descrip- 

 tions and figures of Prasiola crenulata. (Kiitz.) Gay ( = Hormidium crenulatum Kiitz. 

 Phyc. Germ. 1845, p. 193 ; Ulothrix crenulata Kiitz. Tab. Phycol. II, t. 97, f. 2). 



6 Prasiola antarctica Kiitz. 



Spec. Alg. 1849, p. 473 ; Tab. Phycolog, V, t. 40, f. 4 ; Rabenh. Flor. Europ. Alg. 

 Ill, 1868, p. 311. 



Long, thall. 2-4 mm.; lat. thall. 1.5-3 M ; diam. cell. 4-7 /*. (PL XXIV, Figs. 

 10, 11) 



Hob. High moraines on Mt. Erebus, attached to stones. 



Although most of the Prasiolas examined from this Antarctic region were without 

 doubt forms of P. crispa the one on the " high moraines " of Mt. Erebus was different 

 in the growth of its thalli and in the spacing of the cells. The spaces between the 

 cell- groups were wider and the cells themselves were not so closely aggregated. This 

 Prasiola agrees in all essential particulars with that described and figured by Kiitzing 

 as P. antarctica ; and, moreover, the habitat on the moist stones of Mt. Erebus is 

 precisely like that given by Kiitzing (" in rupibus madidis ") for this species, whereas 

 P. crispa was only observed on the ground or submerged. 



Under the circumstances we are compelled to regard the Mt. Erebus specimens as 

 Prasiola antarctica, and to disagree with Wille' s assertion, based on a single Antarctic 



