14 F. E. FRITSCH. 



Forma minor (PL L, fig. 27). 



Cellulis multo minoribus, 7-8 /u- latis, exacte globosis vel moclice anguloso-globosis 

 e mutua pressione, in familiis parvis cellularum fequalium aggregatis intra stratum 

 Phormidii nidulautibus ; membrana eellulao eodem modo quo in typo incrassata ; 

 chromatophora cum pyrenoide. 



This form gives rise to one-layered strata of circular or somewhat polygonal cells 

 of almost uniform size. This going hand in hand with the small dimensions of the 

 cells gives the strata a very characteristic regular appearance, in marked contrast to 

 the generally non-uniform strata of the larger-celled type. The cell-membrane is 

 prominently thickened to the same relative extent as in the larger forms, and the 

 cells have a conspicuous pyrenoid. 



Forma robusta W. and G. S. West, op. cit., p. 276, PI. XXIV., figs. 52-54. 



" (PI. L, figs. 34-35). 



Cellulis majoribus vel multo majoribus, 35-78-100 p, latis, globosis vel distincte 

 ellipsoideis, intra stratum Myxophycearum uidulantibus, solitariis vel saepe dense 

 aggregatis ; membr. cell. 2 5-6 M crassa et lamellosa ; chromatophora saepe distincte 

 parietali, globulis oleariis nullis vel magnis et conspicuis. 



The cells of this form attain immense dimensions and, although ordinarily 

 spherical, as the Wests' figures show them, are sometimes ellipsoidal (figs. 34, 35). In 

 my material the cells of this form generally contained large and conspicuous 

 oil-globules between the membrane and the contents. A pyrenoid does not appear 

 to occur. Occasionally the cell-contents are reddish-brown (cf. above). The outer 

 surface of the wall is frequently somewhat irregular, giving the appearance of flakes 

 of membrane becoming detached. 



Forma filamentosa (PI. L, fig. 28). 



Cellulis globosis vel modice depresso-globosis, 14-20 /A latis, in filamentis brevibus 

 dispositis, intra stratum Myxophycearum nidulantibus, cum pyrenoidibus conspicuis. 

 This form is rare. 



Forma simplex (PI. L, figs. 30, 31, 33). 



Cellulis globosis, 18-35ju, latis, solitariis vel in familiis aggregatis, intra stratum 

 Myxophycearum nidulantibus vel libere natantibus, sine pyrenoidibus, sed cum granulis 

 amylaceis multis. 



This is the form originally described by Messrs. W. and G. S. West. The form 

 with small pyrenoids shown in fig. 32 connects f. simplex with f. typica. 



Forma stellata (PI. L, fig. 29). 



Cellulis globosis, ut in forma typica, saepe ca. 30 /u latis, cum globulis oleariis 

 conspicuis, radiatim circum cytoplasma cellularum dispositis. 



