174 PRBSH-WATER ALG^ OF THE UNITED STATES. 



Syn—M. scalaris, Hassall, Fresh-Water Algae, vol. i. p. 166, et Rabenhorst, Flora Europ. 



Algarum, Sect. III. p. 257. 

 Eab. — 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 yery possibly were not fuUy matured. 



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

 jugate. 



M. parTuIus, Hassall. 



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



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

 Syn.—M. parvulus, Hassal, Fresh-Water Algse, vol. i. p. 169, et Rabjnhoest, Flora Europ. 

 Algarum, Sect. III. p. 251. 



jETaZ).— 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 PLEUROCARPUS, A. Beatjn (1855). 



Cellulse esedem quae in Mesocarpo ; copulatio lateralis et sporifera, nonnunquam genuflexa et 

 plerumque sterilis. (R.) 



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

 mostly sterile. 



P. mirabilis, Braun. 



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

 lievibus. (R.) Species mihi ignota. 



Syn. — Mougeotia genufiexa, Agardh. Bailey, Silliman's Journal. New Series, vol. iii. 



Pleurocarpus mirabilis, A. Bratjn. 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. 



Oeder Siphophyceee* 



Algae unicellulares. Cellula utriculiformis, plerumque ramulosa ; ramuli vegetatione terminali 

 praediti, saspe demum septo discreti, et alteri in oosporangia, alteri in antheridia transmutantur. 

 Cytioplasma, viride, granulosum, mucilaginosum, vesiculis chlorophyllosis et granulis amylaceis 

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



Unicellular algse. 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 zoospores, or by oospores. 



