100 FRESH-WATER ALG^E OP THE UNITED STATES. 



Propagatio duplex ist, aut non sexualis aut sexualis; ilia fit cellulis quibusdara certa distantia 

 intumescentibs, multipartitis, in coenobia filialia intra cosnobiuin matricale evolutis, postea libere 

 erumpentibus; haec cellulis masculis multipartitis in fascicules spermatozoideorum mobilium, con- 

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

 mescentibus, non divisis, sed post feecundationem 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 vacuolcs, 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 ccenobiuru daughter-cceuobia, which are 

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

 into fasciculi of spennatozoids, 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. globator, (LINN.) EHRB. 



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

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

 masculis fascicules spermatozoideorum numerosos rubescentes foventibus (= Sjrfiasrosira 

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

 totidem oosporas globosas rubras episporio hyalino stellato circumdatas foventibus (= Vol- 

 vox stellatus, Ehrb.). (R.) 



Syn. V. globator, (LiNNE,) EHRB. RABENHORST, Flora Europ. Algarum, Sect. III. p. 97. 

 Hab. In stagnis. United States. 



Larger ccenobium, 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 (= Sphaerosplisera 

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

 fecundation, develop into 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. 



OEDER Zygophyceae. 



Algae aut uni- aut psendomulti-cellulares, sine vegetatrone terminal! et ramificatione vera. Cellulaa 

 singulae aut geminatae aut seriatim conjunctae. Multiplicatio fit cellularum divisione in unain direc- 

 tionem. 



Propagatio fit zygosporis conjugatione cellularum similium binarum ortis. 



Algae either uni- or pseudomulti-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 DESMIDIACE^l. 



Algae unicellulares, sine ramificatione vel vegetatione terminal!. Cellula? forma admodum varia, 

 plerumque in medio plus minus profunde constrict et in duas semicellulas symmetrieas <I:vism. 



