PRESII-WATER AhQM OF THE UNITED STATES. Ul 



latis, rotundatis vel siuuato-bi- tricrenatis ; lobo polari abbreviato late truncate, leviter cinai-- 

 ginato, augulis acutis lateraliter plus minus porrectis ; cytioderinate subtilissinie punctate). 



Sijn. — E. hinale, (Turpin) Ralfs, British Dcsmidca;, p. 90. 



Bab. — Florida; Bailey. Pvhode Island, (S. T. Olney,) Thwaitcs. Pennsylvania; Wood. 



Frond very minute, scarcely twice as long as broad, oblong ; segments with their basal ])ortion 

 either entire or bicrcnate at the sides, slightly contracted beneath the ends ; ends dilated, ncit 

 protuberant beyond the angles, its central notch acute, broad ; tr. v. with two lateral infla- 

 tions, end.s truncate, angles rounded. (A.) 



Hemarh. — Fig. 3, pi. 13, represents the front view of a frond, ningnified 750 

 diameters. 



Genus MICRASTERIAS, Ac. (1827). 



Cellulaj compressa3, profunde constrictoe, a frontc orbiculares vel late ellipticre, a vcrticc fusiformcs 

 cum utroquo polo acuto, semicellulae tri- vel quinque-lobaB ; lobi basalcs aut integri aut pluriplicitcr 

 inciso-lobulati ; lobus polaris aut integer aut sinuatus aut emarginatus, et interdum angulis prodiic- 

 tus et bifidus. Cytioplasma chlorophyllacea in celluls lumen subsqualiter <]istriliu1a, granula 

 amylacea sparsa iuvolveus. Cytioderma plerumque la;ve, uonauuquam punctatum, granulalum vel 

 mucronatum. 



Zygosporoe globosas, setate provecta acukis simplicibus, apicc bi- multi- fidis, nonnunquam repetito- 

 multiliidis arniataj. 



Cells compressed, profoundly constricted, viewed from the front orbicular or broadly elliptic, from 

 the vertex fusiform with acute ends. Semicells 3- or 5-hjbed ; basal lobes cither entire or many 

 times incisely-lobulate ; end lobe either entire or sinuate or eraarginato, and sometimes with its angles 

 produced and bifid. Chlorophyllous cytioplasm distributed nearly uniforndy in the cavity of the 

 cell, surrounding scattered starch granules. Cytio<lerui mostly smooth; sometimes punctate; 

 granulate or mucronate. 



Zygospores globose, at maturity armed with simple spines, whose ends bifid or nmllilid, and some- 

 times repeatedly multifid. 



A. Semicellulas (rilohae. Lobi bamles horizonlales ; lobus polaris valcle tlitalafus, dorxo plane 

 convcxus, truncatus vel leoiter relusus, a lobis basalibus sinii amplissimo disc7-elus. 



A. Semicells trilobate. B(i!<(il lubes horizontal ; end lobe strou<jhj dilated, with lite back con- 

 vex, truncate, or slightly retuse. 



M. arciiata, Bailey. 



M. mediocris, quadrangularis, paulo latior quaui longa, profundi; pinnatifida; lobis basalibus 

 angustis elongatis, arcuatis, in apicem acutum attenuatis, divergentibus; lobis i>olaribus 

 angustusimis, utrinque graciliter productis, in apieem acutum attenuatis, in medio dorso 

 modice retusis. (R.) 



Sijn. 31. arcuata, Bailey, Microscopical Observations : Smithsonian Contributions, vol. ii. 



Hab. — In stagnis. Florida; Bailey. 



" Quadrangular, segments three-lobed, the basal lobes long and arcuafe, subtcndcil by the trans- 

 verse projections from the ends of the slightly notched terminal lobes." (Bailey.) 



M. e\pansa, Bailey. 



M. mediocris, tarn longa quam lata, lobis stellatira e.xi)ansis; lobis basalibus angustis in apicem 



acutum attenuatis, divergentibus, rectis; lobis polaribus e basi angusta sensim dilatatis, in 



medio dorso late sinuatis, angulis acutis (sed muticis). (Pv..) 

 Syn. — M. erpansa, Bailey, Microscopical Observations : Smithsonian Contributions, vol. ii. 

 Hab. — In stagnis, Florida; Bailey. 



