FRESH-WATER ALG^ OF THE UNITED STATES. 99 



Ccenobium mobile, globose, subglobose or in square tables, composed of green cells which have 

 two motile cilia and a double contractile vesicle. The common tegument surrounding the coeuobium 

 hyaline, and more or less amplified. 



Propagation either sexual or non-sexual. The sexual monsecious or disecious ; either all or some 

 of the cells of the ccenobium exhibiting male and female characters. The male cells containing 

 spermatozoids, the female finally converted into a quiet oospore. Non-sexual propagation taking 

 place by means of motile gonidia (both macrogonidia and microgonidia, by some called zoogonidia). 

 Macro- and micro-gonidia arising by the simultaneous and repeated division of the cytioplasm ; the 

 first definite in number (2-4-8-16, &c ), the larger, oblong or rounded, with the anterior end more 

 or less rostellate, with two cilia exserted through the membrane of the vesicle, furnished with a cen- 

 tral or parietal red spot, and often with two contractile vacuoles ; the microgonidia indefinite in 

 number, much the smaller, pale or dirty green or luteolous, furnished at the apex with cilia, mostly 

 even within the mother-cell, moving rapidly, and finally escaping on the rupture of the membrane. 



Genus CHLAMYrOCOCCUS, A. Bratjn. 



Cellulae globosse, vel subglobosse (4—8 in ccenobium fugacissimum eonjunctse), cytiodermate sub- 

 crasso firmo, cytioplasmate granuloso, fusco-rubro vel puniceo (in evolutionis gradibus quibusdam 

 in colorem viridem mutato). Macrogonidia 2-4-8, rotundata, polo antico rostriformi producta, duo 

 cilia longissima gerentia, nucleo centrali rubro, globulis amylaceis 4-6, non semper visibilibus 

 instructa, tegumento amplissimo hyalino plerumque ovoideo vestita. Microgonidia multo minora, 

 Dumerosa, luteola vel sordide viridia, apice rubella, ciliis binis instructa, intra tegumentum matri- 

 cali alacriter vaeillantia, denique membranse ruptura elabentia. (R.) 



Cells globose, or subglobose (4-8 conjoined in a very fugitive ccenobium), cytioderm thickish, 

 firm, cytioplasm granular, brownish-red or puniceus, in certain stages of evolution changed into 

 green, Macrogonidia 2-4-8, rounded, the frond end bearing very long cilia, furnished with a 

 central reddish nuclei and with four to six, not always perceptible, starch granules, clothed with a 

 very ample, hyaline, mostly ovoidal tegument. Microgonidia much the smaller, numerous, luteolous 

 orsordid green, the apex reddish, furnished with two cilia, moving actively within the maternal 

 ■-.egument, and at last escaping by the rupture of the membrane. 



Ch. niTalis (Bauer, Ag.). A. Braun. 

 Ch. globulis, 0.004"— 0.00135". (R.) 



Hah. In nive seterna, Greenland. Rocky Mountains. 



Syn. Oh. nivalis (Baue, Ag.). A. Braun. Rabenhorst, Flora Europ. Algarum, Sect. III. 



p.9T. 

 Globules, 0.004"— 0.00135" in diameter. 



Remarhs. — I have never seen any good specimens of this plant, merely some 

 cells mounted in Canada balsam, and therefore ruined for scientific study, which 

 had been collected by Dr. Kane in one of his Arctic voyages. I have also had 

 some indications of plants in a little parcel sent me by Mr. Sereno Watson, who 

 informs me he has seen the red snow very abundant in the higher peaks of the 

 Eocky Mountains. It is a matter of presumption rather than determination, there- 

 fore, that the species is identical with the European. 



Genus VOLVOX, Ehrb. 



Ccenobium exacte spbEericum, continue rotatum et agitatum, globum cavum quasi fingens, e cel- 

 lulis numerossissimis sequali distantia peripherice dispositis, gelatina matricali coiinexis, puncto 

 rubro lateral!, locellis (vacuolis) binis contractibilibus necnon ciliis binis longe exsertis instructis, 

 vesica communi hyalina circumcinctis compositum. 



