474 Journal of Applied Microscopy. 



changed environment. Hence she believes that these internal characteristics of 

 the cells form a surer ground for judging of relationships than any other. Klebs, 

 Artari, and Gay maintain that Plenrococcus vulgaris is a constant form, either 

 unicellular, or forming small, more or less quadrangular cell-complexes, without 

 pyrenoid, and with a chromatophore lining the whole cell-membrane. But 

 Chodat includes in this species forms with and without pyrenoid, and with either 

 parietal or stellate chromatophore. On account of the general observation 

 stated above, the work is in accord with that of Klebs, Artari, and Gay. But forms 

 are found which, in the unicellular condition are hard to distinguish from Plenro- 

 coccus vulgaris, and which do produce filaments when placed in a liquid medium. 

 However, these forms cannot be called Plenrococcus vulgaris, since in them the 

 chromatophore lines only a part of the cell-membrane, and they possess pyre- 

 noids. There is also a remarkable physiological difference between the true 

 species and these filamentous forms ; the former soon dies in Knop's solution, 

 while the latter live indefinitely therein. Thus these filamentous forms are to be 

 classified, not as Plenrococcus vulgaris, nor — considering the pyrenoids — as 

 Plenrococcus at all, but are to be put into another genus, and since these fila- 

 ments have not produced zoospores, the writer believes it to be better to create 

 a new genus for them than to follow Klebs, and put them iuto the genus Stigeo- 

 clonium. For this new genus she suggests the name Pseudo-Pleurococcus, and 

 gives descriptions of two species under it. 



The genus Pseudo-Pleurococcus Snow is made up of forms which, in the 

 atmosphere, are either unicellular, or form parenchymatous masses ; in liquid 

 media they form filaments. The chromatophore lines a part of the cell-mem- 

 brane, but not all. Pseudo-Pleurococcus botryoides Snow was found on tree 

 trunks near Ann Arbor, Michigan, while Pseudo-Pleurococcus vulgaris Snow was 

 gathered from a similar habitat in Basel, Switzerland. The main differences 

 between the two species are these : in the former the branches arise laterally 

 on the filaments, in the latter they originate by a forking of the terminal cell ; 

 in the atmosphere, the former produces larger cell-complexes ; and in nutrient 

 solution the former branches more profusely. The article is accompanied by a 

 colored plate, showing various forms of both new species. 

 University of Chicago. B. E. LIVINGSTON. 



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