028 DH. Е, К. FRITSCH ON FRESHWATER ALGAE 
20. CigtAsTRUM. MICROPORUM, Näg. ee Л. Bre Aly. unicell, 1895, p. 10 ; 
Rabenh. Fl. Europ. Alg. iii. 1868, p. 80. 
Samples 10, 11, 15; fairly common. 
20 и. CELASTREM MICROPORUM, №. forma IRREGULANE, P. [Lo Fritsch, 
(Text-fig., H, p. 323.) 
Cellule ecenobii irregularissime coherentes. 
In sample по. 11 there occurred side by side with normal colonies of 
C. тѓеторотит others in which the eells were very irregularly connected, зо 
that the compact spherical appearance of the normal colony was often quite 
lost. Frequently the sphere was only half formed ; in other cases, while 
several cells of the colony showed the usual arrangement, others were хо 
arranged that they stood off from the general surface of the colony and 
completely destroyed the symmetrical character of the latter (text-fig., H). 
In other cases, again, the colonies were very small, consisting of only 4 or 6 
cells. These peculiar forms may possibly be explained by Senn’s observations 
(* Ueber einige coloniebildende einzellige Algen," Bot. Zeitung, lvii. 1899), 
who found that colonies of Cælastrum tend to dissociate into their individual 
cells if plenty of oxygen is present in the surrounding medium. This is 
likely to be the case in water in these Antarctic localities and may account 
for the numerous irregularities above described. Samples 10, 11, and 14 
contained numerous isolated cells of the Cirlastrum-type, and these are very 
probably to be regarded as dissociation-produets of normal colonies. 
21. CELASTRUM spHaricum, Naeg. Gatt, einzell. Algen, Zürich, 1849, р. 98 
& tab. 5c. Но. 1. 
Sample 11, rather rare. 
PLEUROCOCCACEZTE. 
29. PLEUROCOCCUS VULGARIS, Menegh. Monograph. Nostoch, р. 98. 
Samples 1 and 3 (yellow snow 1), rare ; samples 10 and 11, not uncommon, 
This species was oceasionally found in nos. 10 and 11 forming short 
filaments. 
23. РиоторквмА Browsu, А. №. Fritsch. (РІ. 10. fig. 1 : Pl. 11. phots. 1, 
2,3, 5, Р.) 
Thallus constat ex uno vel duobus (vel pluribus ?) stratis cellularum et 
explanatus est in summa nive; margo thalli irregularis. Се mult- 
angulares vel angulis modice rotundatis; membrane cellularum gelatinose (?), 
hyaline, lamellosie, lamella intermedia paulum granulata. Chromatophora 
singula, similis disco arcuato, cum pyrenoide. Cellule interdum continent 
aliquantum adipis, Propagatio ? 
Diam. of cells —5-12 и. 
