174 FRESH-WATER ALOJE, OF THE UNITED STATES. 



Syn. M. scalaris, HASSALL, Fresh-Water Algae, vol. i. p. 1G6, et RABENIIORST, Flora Europ. 

 Algarum, Sect. III. p. 257. 



Hab. In fossis, prope Philadelphia. 



Sterile cells 3-6 times longer than their diameter, fertile strongly curved ; zygospores oval. 



Remarks. This species is abundant in the stagnant ditches near Camden. It 

 agrees well with the descriptions of the European form. I have, however, never 

 seen it in the state in which it has " fuscous spores." They have always been 

 greenish, but very possibly were not fully matured. 



Fig. 5, pi. 15, represents a pair of cells of this species just commencing to con- 

 jugate. 



M. par vu Ins, HASSALL. 



M. cellulis diametro (0.00031" 0.00041") 5-12 plo longioribus; zygosporis globosis, plerumque 

 0.00062" latis, sporodermate fusco Isevi. (R.) Species mihi ignota. 



Syn. M. parvulus, HASSAL, Fresh-Water Algae, vol. i. p. 169, et RAB^NHORST, Flora Europ. 

 Algarum, Sect. III. p. 257. 



Hab. Rhode Island ; (S. T. Olney) Thwaites. 



Cells 5-12 times longer than their diameter (0.00031" 0.00041") ; zygospores globose, mostly 

 0.00062" broad, spore coat fuscous smooth. 



Genus PLEUROCAKPUS, A. BRAUN (1855). 



Cellular eaedem qua? in Mesocarpo ; copulatio lateralis et sporifera, nonnunquam genuflexa et 

 plerumque sterilis. (R.) 



Cells like those in Mesocarpus; conjugation lateral and sporiferous, somewhat genuflcxuous and 

 mostly sterile. 



P. mirabilis, BRAUN. 



P. cellulis diametro (0 0011" 0.0013") 2-5 plo longioribus; zygosporis subglobosis, fuscis, 

 Irevibus. (R.) Species mihi ignota. 



Syn. Mougeotia genuflexa, AGARDH. BAILEY, Silliman's Journal. New Series, vol. iii. 



Pleurocarpus mirabilis, A. BRAUN. RABENHORST, Flora Europ. Algarum, Sect. III. p. 

 258. 



Hab. West Point, New York; Providence, Rhode Island ; Detroit, Michigan ; Fort Winne- 

 bago, Wisconsin ; Bailey. 



Cells 2-5 times longer than their diameter (0.0011" 0.0013") ; zygospores subglobose, fuscous, 

 smooth. 



ORDER Si phopll \<'C;r. 



Algse nnicellulares. Cellula ntriculiformis, plerumque ramulosa ; ramuli vegetatione terminal! 

 praditi, ssepe demum septo discreti, et alteri in oosporangia, alter! in antheridia traiismutantur. 

 Cytioplasma viride, granulosum, mneilaginosum, vesiculis chlorophyllosis et granulis atnylaccis 

 repletum. Propogatio fit aut cytiogenesi libera, aut zoogonidiis aut oosporis. 



Unicellular algae. Cells utriculiform, mostly branched ; branches with a terminal vegetation, 

 often finally cut off by a partition wall and transformed into antheridia or oosporangia. Cytioplasm 

 green, granular, mucilaginous, filled with chlorophyl vesicles and starch granules. Propogation 

 either by forming minute spores by free cell formation, or by zoosporcs, or by oospores. 



