FRESHWATER ALG.E 277 



Hob. Blue Lake. 



These are the largest Pleurococcus cells we have yet seen. 



13 Pleurococcus dissectus (Kiitz.) Nag. 



Gatt. einzell. Alg, 1849, p. 65, t. 4, f. 3; Protococcus dissectus Kiitz. Spec. Alg. 

 1849, p. 199 ; Tab. Phyc. p. 4, t. 3. 



Diam. cell. 4.5-9 p. (usque ad 16 n in cellulis solitarus). (PI. XXIV, Figs. 30-39) 



Hab. Ponds on Mt. Erebus, attached to tire -tough sheets of Lyngbya Erebi. 

 Green Lake, among Ulothrix ccqualis forma. Blue Lake and Deep Lake, attached to 

 the sheets of Myxophycese. 



The specimens agreed well with forms of this species, and especially with the 

 figures given by Suringar (Observ. Phyc. in Flor. Batav., Leovardice, 1857, p. 56, t. 4, 

 f. D) of "Protococcus dissectus /3 cuneata." They were, however, submerged (though 

 frozen), whereas the usual habitat of PI. dissectus is a subaerial one., The division of 

 the cells, partly radial, partly tangential, and partly oblique, is very characteristic. 



This species often forms a one- layered stratum, in which the cells remain angular 

 by compression. This condition is almost a definite state of the plant. (Vide 

 PI. XXIV, Fig. 39). 



Genus TKOCHISCIA Kiitz. 



14 Trochiscia aspera (Reinsch) Hansg. 



In Hedwigia, 1888, p. 128 ; G. S. West, Treatise Brit. Freshw. Alg. 1904, p. 303, 

 c. figs. 82 A-F. Acanthococcus aspera Reinsch, 1886. 

 Diam. cell. 15.5-22 M. 

 Hab. Green Lake. 



PALMELLACE.E. 



Genus GLCEOCYSTIS Nag. 

 15 Gloeocystis sp. 



Diam. cell. 5-12 ^, c. integ. gelat. 14-30 /j.. 



Hob. In pond, Cape Royds. 



From the available material it is not possible to exactly identify this Alga. Wille 

 has recently accepted certain views of Gerneck, and stated that the various Algse 

 included in Nageli's genus Gloeocystis are merely developmental stages of other green 

 Algse (c/. Wille in Engler and Prantl, Naturlich. Pflanzenfam. Chloropliycece, 1909, 

 p. 31). This view we do not entirely accept, as there is no positive proof that all 

 these Algse are states of species belonging to other genera, and Gerneck' s experience 

 is much too limited to warrant such a wide statement. This is the more emphasised 

 when one finds that some of Gerneck' s recently proposed genera can scarcely be 

 regarded as specifically distinct, let alone as valid generic types. 



The greatest suspicion always attaches itself to Algse found only in culture 

 vessels. Such forms may in many cases be mere states of other Algse which remain 



