124 FRESH-WATER ALG^ OF THE UNITED STATES. 



Sph. serratum, Bailet. 



Sph. cellulis diametro dnplo brevioribus, profunde et acute exeisis, arete conjunctis ; lobis 

 ntrinque cuspidatis, paulum conniventibus ; isthmis nullis ; vagina crassa. (R.) 



Syn. — Sph. serratum, Bailet, Micros. Observation. Smithsonian Contributions, 1850. Cum 

 icone. 



Hah. — South Carolina ; Georgia ; Florida ; Bailey. 



" Joints broader than long, deeply notched or divided into two transverse portions with acute 

 projecting ends, which give a serrated outline to the chain." Bailey. 



Genus HYALOTHECA. 



CellulaB brevsB, cylindricse, medio non profunde constrictsB, a latere diseiformes, in fila confervacea 

 sine isthmis arete conjanctae et vagina mucosa ampla achroa inclusee. Massa chlorophyllosa in 

 qnaque semicellula 4-8, 5-10 radiata. 



Cells short, cylindrical, not profoundly constricted in the middle, disciform in the end view, 

 closely united without intervening isthmuses into a confervoid filament, which is inclosed in an 

 ample mucous sheath. Chlorophyl masses in each cell 4-8, 5-10 radiates. 



H. disilliens, (Smith) Br£b. 



H. fasciis praelongis ; cellulis oblongo-quadrangularibus, diametro snb-duplo brevioribus, inter- 

 dum ante divisionem subsequalibus, angulis nounihil rotundatis, plerumque medio obsolete 

 constrictis, saepe hand constrictis. 



i?zam— 0.00089"— 0.00098". (R.) 



Syn. — H. disilUens, (Smith) Breb. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 152. 



Hob. — South Carolina ; Florida ; Rhode Island ; Bailey. Rhode Island (S. T. OIney), 

 Thwaites. Pennsylvania ; Wood. 



Filament very long, cells oblong, quadrangular, about one-half as long as broad, sometimes before 

 division as long as broad, angles somewhat rounded, mostly obsoletely constricted in the 

 middle, often not constricted. 



BemarJcs. — The specimens which I have identified as H. disilUens, agree with 

 the various figures and descriptions of the European form, in every thing except 

 that in many cases there is no constriction whatever in the centre of the cell, and 

 when the constriction does exist, it is never so pronounced, as some of the descrip- 

 tions indicated. The plant is very common about Philadelphia, growing in springs 

 and ditches. 



Fig. 12, pi. 12, represents this part of a filament of this species. 



H. mncosa, (Meet.) Eheb. 



H. fasciis confervaceis, minus fragilibus ; cellulis quadrangularibus, diametro sequalibus vel 

 Bubaequalibus, medio non constrictis, ad utrumque finem (annuliformi-bicarinatis) bidentatis. 

 (R.) Species mihi ignota. 



Diam.—O.OOOtS"— 0.0008". (R.) 



Syn. — Gloeoprium mucosum, Hassal, Fresh Water Algae, p. 346. 



H. mucosa, (Meet.) Eheb. Rabenhoest, Flora Europ. Algarum, Sect. III. p. 132. 

 /Tab.— Rhode Island ; (S. T. Olney) Thwaites. 



Filament scarcely fragile, mucous sheath very broad ; joints about as broad as long, not con- 

 stricted, but having at one of the ends a minute bidentate projection on each mlrgin, the 



