144: FRESH-WATER ALGJE OF THE UNITED STATES. 



Syn. M. ringens, BAILEY, Microscopical Observations, pi. 1, fig. 11: Smithsonian Contri- 

 butions, vol. ii. 

 Hob Florida; Bailey. 



Oblong, segments three-lobed, coarsely granulated near the edge ; basal lobes subdivided by a 

 deep notch into two rather broad and obtuse or slightly bidentate projections ; terminal lobes 

 exserted, emarginate ; extremities bidentate or obtuse. 



* * Semicellulee quinque-lobatae. 



* * Semicells 5-lobed. 



M. truncata, (CORDA) BEEB. 



M. magna, orbicularis, aut Isevis aut snbtiliter punctata ; scmicellulis quinquelobis, lobis inter 

 se sinu obtusangulo subangusto discretis, basalibus et interuiediis inciso-lobulatis, segmentis 

 acute bidentatis; lobo polari late cuneato, in dorso truncate, m'odo leviter convexo, modo 

 leviter retuso, angulis aut bidentatis aut integris. (R.) 



Diam. 0.003" Long. .0036". 



Syn. M. truncata, (CoRDA,) BREBISSON. RABENHORST, Flora Europ. Algarum, Sect. III. p. 

 191. 



Hab. Georgia ; Florida ; Rhode Island ; Bailey. Pennsylvania ; Wood. Rhode Island 

 (S. T. Olney) ; Thwaites. 



Frond orbicular, smooth ; segments 5-lobed ; basal and middle lobes obscurely bipartite, ex- 

 tremities bidentate ; end lobe very broadly cuneate, bidentate at the angles, and with a slightly 

 central concavity. (A.) 



Remarks. The dimensions given above were taken from the largest specimens 

 I have seen, but do not at all equal those given by Prof. Rabenhorst, his breadth 

 is .OOil". According to the same authority, M. crenata, Breb., is merely a variety 

 of this species. 



Fig. 15, pi. 21, represents the outline of a frond of this plant. 



M. furcata, Aa. 



M. permagna paulo longior quam lata, levis ; semicellulis quinque lobis (paene 7-lobis) ; lobis 

 omnibus rectis ; lobis basalibus angustioribus, bilobulatis, lobulis bifidis, sinu obtusangulo 

 vel acutangulo, segraentis linearibus bidentatis (denticulis ssepe inrequilongis) ; lobis inter- 

 mediis duplo latioribus, inciso-bilobis, lobulis iisdem ac loborum basalium ; lobo polari non- 

 nihil anguste cuneato, prominulo, in apice plus minus profunde sinuato-vel undulato iuciso, 

 angulis bidentatis. 



Diam. 7 |g/ = -008". 



Syn. M. rotaia, RALFS, British Desmidiese, p. Tl. 



M. furcata, AGARDU. RABENHORST, Flora Europ. Algarum, Sect. III. p. 191. 



Hab. South Carolina ; Georgia ; Florida ; Rhode Island ; Bailey. New Jersey ; Wood. 



M. very large, a little longer than broad, smooth ; semicells 5-lobed (scarcely 7-lobed) ; lobes 

 all straight ; basal lobe narrower than the intermediate, bilobulate, lobules bifid, their sinuses 

 acute or obtuse, segments linear, bidentate ; teeth often long and unequal ; intermediate lobes 

 twice as wide as the basal, bilobate, their lobules of the same form as the basal lobe ; end 

 lobes narrowly cuneate, prominent, more or less profoundly sinuately or undulately cut at 

 the apex, angles bidentate. 



Remarks. According to Rabenhorst and others, there is a European form of 

 this species in which the marginal teeth are wanting. This may exist in this 



