16 



MEMOIRS OF THE 2vEW YORK BOTANICAL GARDEN 



the genera Protococcus or Pleurococcus. All of these have since 

 been very generally recognized as belonging to Chroococciis. 



Xaegeli's conception of the genus as set forth in his diagnosis 

 and in his discussion which follows seems to have been of a 

 group whose cells exist either singly or, by division "in alien 

 Richtungen des Ramnes" and remaining for a time intact, be- 

 come associated into small, sjjherical or cuboidal families, or 

 colonies of 2 — 8 or, more rarely, 16-32 cells, surrounded by a 

 thin colorless, homogeneous or at times slightly lamellose wall. 

 Although Xaegeli states that the wall is thin, scarcely one-third 

 the thickness of the lumen of the cell (a thick wall as compared 

 to the cell proper) he undoubtedh" meant thin as compared to 

 that of Gloeocapsa, which he discusses in connection with Chroo- 

 cocciis, and which may become several times thicker than the 

 lumen of the cell. 



The genus Gloeocapsa was proposed by Kuetzing in 1843.'' 

 He designated no type species, but the first species mentioned is 

 G. montana, which may ordinarily be considered the type of a 

 genus when no special one is proposed. His diagnosis of the 

 genus is very brief and incomplete. In 1846,* he illustrated the 

 species. 



The genus was reviewed by Xaegeli {loc. cit.), Avho desig- 

 nated as the type G. at ra ta Kuetz., which he redescribed and 

 illustrated. I have examined bits of the type of both of these 

 species and judging from these and from the descriiDtions and 

 figures given by Kuetzing and Xaegeli, both writers had prac- 

 tically the same conception so far as the type, G. atrata, is con- 

 cerned. As pointed out by Xaegeli and by subsequent writers, 

 the two genera Chroococciis and Gloeocapsa undoubtedly over- 

 lap, and such forms as G. montana seem as clearly allied to the 

 one as to the other. I am considering forms with a firm, smooth, 

 hyaline wall, or tegument, Avith relatively few cells in a colony, 

 and these remaining angular after division throughout the 

 greater part of the life cycle of the colony, and such forms as 

 remain within special teguments for several generations all re- 

 maining within a common, more or less gelatinous, original, 



3 Phycologia Generalis. 



* Tabulae Phyeologicae, 1 : yl. 19. f. III. 



