174 FRESTI-WATER A L G .E OF THE UNITED STATES. 



Syn.—M. scalaris, Hassall, Frcsli- Water AlgK, vol. i. p. lOG, et Rabenhorst, Flora Europ. 



Algarum, Sect. III. p. 257. 

 Ilab.— 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 

 ao-rees well with the descriptions of the European foriii. 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. parviiliis, Hassall. 



M. ccllulis diametro (0.00031" — 0.00041") 5-12 plo longioribus ; zygosporis globosia, plerumqiie 

 0.00002" latis, sporodermate fusco Itevi. (R.) Species mihi ignola. 



Syn. — 31. parvulus, Hassal, Fresh-Water Algoe, vol. i. p. 1G9, et Rabenhorst, Flora Eunip, 

 Algarum, Sect III. p. 257. 



Baft.— 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. Braun (1855). 



Cellula3 eaedom quis in Mesocarpo ; copulatio lateralis et sporifera, nonnunquam gennflexa et 

 plerumque sterilis. (R.) 



Cells like those in 3Iesocarpus ; conjugation lateral and sporiferous, somewhat genuflexuous and 

 mostly sterile. 



P. inirabilis, Braun. 



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

 iKvibus. (R.) Species mihi irjnola. 



Syn. — llougeolia genuflexa, Agardh. Bailey, Silliman's Journal. New Series, vol. iii. 



Pleurocarpus mirahilis, A. Braun. Rabenhorst, I'lora Europ. Algarum, Sect. III. p. 

 258. 



Hah. — 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, fnscoiis, 

 smooth. 



Order Siphophycese. 



Alga unicellulares. Cellula utriculiformis, plerumque ramulosa ; ramuli vegetatione tcrminali 

 prajditi, saepe demum septo discreti, et alteri in oosporangia, alteri in antheridia transuiutantiir. 

 Cytioplasraa viridc, granulosum, mucilaginosum, vesiculis chlorophyllosis et granulis amylaceis 

 replctum. Propogatio fit ant cytiogenesi libera, aut zoogonidiis ant 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 zoospores, or by oospores. 



