FRESH-WATER ALG^ OF THE UNITED STATES. 123 



Remarks -The only specimens that I have seen of this species were found in a 

 spring in the Philadelphia City Park, near Columbia bridge. 

 Fig. 11, pi. 12, was drawn from one of these specimens. 



Genus SPHtEEOZOSMA, Cokda. 



Cellute compress^, medio transversim profunde incise, itaque bilobatae, in quoque lobo massa 

 chlorophyllosa quadnrad.ata nugleum amylaceum involvente pr^dite, in filum planum t^niiformem 

 literahter isthmis conjunctaB. Zygosporae globose vel orales, glabrse. (R.) 

 Syn. — Isthmosira, Ktz. 



Odontellse, spec, Ehrb. 

 Isthmiae, spec, Meneq. 

 Spondylosium, BeSb. 



Cells compressed, transversely very deeply incised in the centre and therefore bilobate, furnished 

 in each lobe with a quadriradiate mass of chlorophyl surrounding a starch grain, conjoined laterally 

 by isthmuses in a tseniform fascia. 



Remarhs.—l have never found any species of this genus in America. Professor 

 Bailey has, however, detected the following: — 



Sph. excaTatum, Balfs. 



Sph. plerumque nudum (sine tubo mucoso) sph. vertebratum multo minus ; cellulis diametro 

 duplo-longioribus, medio excavato-constrictis, a latere ellipticis utroque polo rotundatis; lobis 

 brevibus truncato-rotundatis, laevibus vel granulato-denticulatis ; isthmis binis parvis verru- 

 ciformibus ; zygosporis plerumque ovatis. (R ) 



Latit. filor. 0.0004T"— 00032". (R.) 



Syn. — Sph. excavatum, Ralfs, British Desmids, p. 6T. 



Eab. — Florida ; Georgia ; South Carolina ; Rhode Island ; Bailey. 



"Joints longer than broad, having a deep sinus on both sides and two sessile glands at each 

 margin at their junction, very minute, seldom more than twenty-five joints in the filament, 

 which is fragile, and finally separates into single joints ; at their junction, in the front view 

 are two minute glands or processes, situated one near each angle, and nearly invisible before 

 the escape of the endochrome. The joints are nearly twice as long as broad and much con- 

 stricted in the middle ; the constriction is like an excavation or broad sinus on each side, so 

 that the margins of the filaments appear sinuated. The endochrome is pale bluish-green 

 with minute scattered granules. The transverse view is oblong with four sessile glands, two 

 on each side and situated near the ends." — Ralfs' Brit. Desm., p 67. 



Sph. pnlchrum, Bailey. 



Sph. cellulis oblongo-quadrangularibus, diametro duplo-brevioribus, acute incisis, arete con- 

 nexis ; lobis oblongis rectis, apice rotundatis ; isthmis nullis, vagina mucosa ampla dis- 

 ncta. (R.) 



Syn. — S. pulchrum, Bailey. Ralfs, British Desraid., p. 209 (Cum icone). 



Eab. — West Point, New York ; Princeton, New Jersey ; Bailey. 



" Joints twice as broad as long, deeply incised on each side ; junction margins straight, con- 

 nected by short bands." 



RemarTe. — " Prof. Bailey informs me that this species is twice as large as Sph. 

 vertebratum" Ralfs. 



