86 FRESH-WATER ALG^ OF THE UNITED STATES. 



Propagatio fit gonidiis, quK intra cellulam matricalem cytiogenesi libera oriuntur et dnplicis iniiolis 

 sunt; altera majora, quse macrogonidia, altera minora quse microgouidia dicuntur ; iila oblonga, polo 

 antieo plerumque rostelliformi-producta, pallidiora, ciliis vibratoriis praedita, polo postico truncato- 

 rotundata, obscure viridia, individuum propagant ; hffic forma similii, itidem mobilia, brevi postea 

 in statum quiescentem transeunt, druique in sporas perdurantes {Hypnosporas, Beaun) transmu- 

 tantur. (R.) 



■Unicellular algs, in the strictest sense of the word, chlorophyllous, without terminal growth or 

 true branching, without a vegetative generation of cells. They live either single, segregate, or con- 

 sociated into families. The cells of these families, either indefinitely increasing in number (then 

 families in the true sense of the term), or of definite number (then forming a coenobium). 



Propagation by means of gonidia arising within the mother-cell by free cell-formation ; gonidia of 

 two kinds; the one larger, macrogonidia — the other smaller, mierogonidia ; the former oblong, 

 mostly produced into a pale bicilate beak anteriorly, rounded and greenish at their hinder end, 

 developing into the individual plant ; the mierogonidia similar to these and also motile, but passing 

 after a short time into a quiescent state, and at last into resting spores or hypnospores. 



Genus PROTOCOCCUS, Ag. 1824. 



Cellulae sphaeroideas, segregatse, cytiodermate tenui, hyalino, absque tegumentis, libere natantes 

 vel extra aquam in stratum tenue pulvereum cumulatse. Cytioplasma initio homogeneum, deuique 

 granulosum, viride vel rubellum. 



Spheroidal cells, segregate, cytioderm thin, hyaline, without integument, swimming free or col- 

 lected out of water into a thin pulverulent stratum. Cytioplasm in the beginning homogeneous, 

 finally granular, green, or reddish. 



Remarlcs. — I have introduced this genus as given by Professor Rabenhorst in 

 his Flora Europsea Algarum for the purpose of describing a little plant, upon which 

 I have made some observations. As the notes were originally drawn up as a de- 

 scription of a species, I leave them in that form. I believe it has never before 

 been described, 



Protococcus, (sp. nov. ?) 



P. aquaticus ; cellulis globosis vel angulis, viridibus in stratum pulvereum cumulatis vel in fami- 

 lias arete conjunctis; cytiodermate plerumque distincto ; sporis rotundatis, tegumentis duobus 

 vel tribus protectis ; tegumentis externis, crassibus ; zoogonidiis ovalibus, vel subrotundatis, 

 vel subellipticis, ciliis duobus instructis. 



Z>wm.— Max. spor. perdurant. 7/^^" = .00093"; microg. 75%/ = .00053". 



Aquatic ; cells green, globose or angular, accumulated in a green pulverulent stratum, often 

 closely united into families ; cytioderm mostly not distinct ; resting spores round with two or 

 three thick coats ; zoospores oval or roundish, or somewhat elliptical, furnished with two 

 cilia. 



RemarJes. — I found this species growing in a spring near Hestonville, West 

 Philadelphia, in the month of March. The large winter spores are round, with 

 thick coats. Except in one instance, in which the color was a decided reddish- 

 brown, all that I have seen have been green. How they are produced I do not 

 know. The history of their development into the plant appears to be as follows : 

 The first change is the rupture of their outer thick coat (fig. 4 &, pi. 7) from which 

 the spore finally escapes still clothed with a coat of moderate thickness. The 

 green contents next divide into a number of oval bodies (fig. 6 6, pi. 7) which 



