100 FRESH-WATER ALG^ OF THE UNITED STATES. 



Propagatio duplex ist, aiit non sexualis aut sexualis; ilia fit ci-llulis quibusdam certa distantia 

 iutumescentibs, nmUipartitis, iu cojiiobia filialia iutra coeiiol)ium niatricale evolutis, postea lihere 

 erumpentibus- lioec cellulis masculis multipartitis in fascicules spermatozoideorum mobilium, con- 

 tractiliuui, pyriformium, ciliis binis instructorum, postea liberorum evolutis; cellulis femineis intu- 

 mesceiitibus, nou divisis, sed post foecundationem in oosporas immobiles episporio duplici tircum- 

 datas postremo rubras evolutis. (R.) 



Coenobium exactly spherical, continually rotating and agitated, looking like a hollow globe, 

 composed of very numerous cells, which are arranged on the periphery at equal distances, and are 

 connected by the maternal jelly, and surrounded by a common hyaline bladder; they are also fur- 

 nished with a lateral red point, with two contractile vacuoles, as well as two long exserted cilia. 



The propagation is both sexual and non-sexual. In the latter, certain distant cells enlarge greatly, 

 divide into numerous parts, and evolve within the parent coenobium daughter-ccenobia, which are 

 finally set free. In the sexual propagation certain molecular cells undergo a multipartite division 

 into fasciculi of spermatozoids, which are motile, contractile, pyriform, and furnished with two 

 cilia; the feminine cells are enlarged, and do not undergo division, but after fecundation develop into 

 immovable oospores, which are finally red, and are surrounded by a double episporium or coat. 



V. $!^lobator, (Linn.) Ehrb. 



V. coenobiis majoribus ad ^"', cellulis numerossissimis (ad 12,000); ccenobiis filialibus semper 

 octo intra matricale fructificatione non sexuali evolutis ; fructificatione dioica ; coenubiis 

 masculis fasciculos spermatozoideorum numerosos rubescentes foventibus (^ Sphxronira 

 volvox, Ehrb.); cffinobiis femineis cellulas sexuales (oogonia) 20-40 post fcecuudationem in 

 totidem oosporas globosas rubras episporio hyaliuo stellato circumdatas foventibus (= Yol- 

 vox stellatus, Ehrb.). (R.) 



Syn. — F. globalor, (Linne,) Ehrb. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 91. 



Hah. — In stagnis. United States. 



Larger coenobium, about ^" in diameter, composed of very numerous (about 12,000) daughter- 

 ccenobia, always 8 within the maternal one, evolved without sexuality; fructification dioe- 

 cious ; male coenobium giving origin to numerous reddish spermatozoids (= Sphffirospliaera 

 Volvox, Ehrb.); female coenobium, giving origin to from 20-40 sexual cells, which, after 

 fecundation, develop juto the same number of globose red oospores surrounded by a stellate 

 hyaline episporium. 



Remarks. — Some of my friends tell me they have found this species abundantly 

 around Philadelphia. I have not been so fortunate, and have seen but a few 

 scattered specimens, which have afforded no opportunity of studying their deve- 

 lopment and life-history. 



Order Zy^Topliyceae. 



Alga; aut uni- aut pseudomulti-cellulares, sine vegetatione terminali et ramificatione vera. Cellulse 

 singula aut geminatae aut seriatim conjunctaj. Multiplicatio fit cellularum divisione in unam direc- 

 tionem. 



Propagatio fit zygosporis conjugatione cellularum similium binarum ortis. 



Algae either uni- or pscudomulti-cellular, without terminal growth or true branches. Cells segre- 

 gate or geminate, or arranged in a single row. Multiplication taking place by a division of the 

 cells in one direction. 



Propagation by zygospores, formed by the conjugation of two similar cells. 



Family DESMDIACE^. 



Alga; uniccllulares, sine ramificatione vel vegetatione terminali. Cellulaj forma admodum varia, 

 plerunique iu medio plus minus profunde constrictie et in duas semici^llulas svmuietrica.s Cm>-v^. 



