PRESH-WATER ALG^ OE THE UNITED STATES. 13 



cells, each of which has a distinct tegument, the whole being surrounded with that of the old mother- 

 cell. This process of division is then repeated again and again, the original cell-wall remaining and 

 surrounding the family thus formed. Cytioderm thick, often very thick, equalling, or exceeding in 

 diameter the cavity of the cell, achromatic or colored, mostly lamellated, lamellae or strata not rarely 

 separating. Cytioplasm of various colors, aBruginous, bluish-green, chalybeate, reddish, yellowish- 

 fuscous, &c. Division of the cells occurring in three directions. The last generation of cells smaller 

 than the earlier ones. 



G. sparsa, Wood. 



G. in strato mucoso sociis algis variis sparsa ; cellulis sphaericis, vel oblongis vel ovatis, 2-8 in 



familias consociatis ; familiis subglobosis vel subovatis, interdnm numeroso-aggregatis ; tegu- 



mentis internis aureofuscis, firmis, rarissime coloris expertibus, homogeneis, vel lamellosis; 



teguraentis externis achromaticis, rare subachromaticis, plerumque vix visibilibus ; cytioplas- 



mate homogeneo. 

 Diam. — Max. cell, oblong, sine tegum. long., ^^Vty") ^^^-i Trios" 'i cell, glob., sine tegum., 



siss"; ciim tegum., t^Vf"; fam., ^1/'- 



Syn. — G. sparsa, Wood, Prodromus, Proc. Amer. Philos. Soc, 1869, 123. 



Hab. — In rupibus irroratis prope Philadelphia. 



G. scattered in a mucous stratum composed of various algse ; cells spherical, or oblong, or ovate, 

 associated together in families of from 2-8; families subglobose or subovate, sometimes aggre- 

 gated together in large numbers ; inner tegument yellowish-brown, firm, rarely colorless, homo- 

 geneous or lamellate ; external tegument achromatic, rarely subachromatic, generally scarcely 

 visible. 



RemarTcs. — This species was found in a rather firm, grumous or gelatinous coat- 

 ing of a light brown color, growing on the rocks at Fairmount Water Works, 

 chiefly composed of a very minute nostochaceous plant, but contained numerous 

 other algse. The color of the tegument is yellowish-brown, sometimes with some 

 red in it, sometimes with something of a greenish tint. This inner colored coat 

 is not generally more than once or twice lamellate, often it is not at all so. This 

 species seems somewhat allied to 0. styophila, but differs slightly in the form of 

 the cell, and more especially in not having a distinct thallus, and in the families 

 being small and containing but few cells. 



Fig. 7, pi. 8, represents this species, magnified 750 diameters. 



Genus CtELOSPH^EIUM, N^geli. 



Thallus parvus, e cellulis minimis in familias periphericas consociatis vel in stratum periphericum 

 simplex et in muco teguraentis celerrime confluentibus formato nidnlantibus compositus. Cellu- 

 larum divisio, initio generationum serierum, in omnem fit directionem, tum denique alternatim 

 ad superficiei sphsericse utramque directionem. 



Thallus small, composed of very small cells consociated into peripheral families, or in a simple 

 peripheral layer, inclosed in their quickly confluent teguments. Division of the cells at first in all 

 directions, afterwards only in each direction on the surface of the sphere. 



C. dubinm, Geun. ? 



i C. thallo microscopico, subgloboso vel e&orme, natante, congregato; cellulis globosis aut sub- 

 globosis; cytioplasmate pallide serugineo, subtiliter granulato. 



Diam.— Cell, plerumque ^-^Vir" = -00016"; rare 5^^^" = .00025"; fam. tsAif"— tjVtju" = 

 .00083"— .0033". 



