100 FRESH-WATER ALG^ OF THE UNITED STATES. 



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

 intumescentibs, muUipartitis, in ccsnobia filialia intra coenobium matricale evolutis, postea libere 

 erumpentibus; hsec cellulis masculis multipartitis in faseiculos spermatozoideorum mobilium, con- 

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

 mescentibus, non divisis, sed post foecundationem in oosporas immobiles episporio duplici circum- 

 datas postremo rubras evolutis. (R.) 



CcEnobium 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. globator, (Linn.) Ehbb. 



V. coenobiis majoribns ad ^"', cellulis numerossissimis (ad 12,000); coenobiis fllialibus semper 

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

 masculis faseiculos spermatozoideorum numerosos rubescentes foventibus (= Sphaerosira 

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

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

 vox stellatus, Ehrb.). (R.) 



§yn. — F. glohator, (Linne,) Ehrb. Rabenhorst, Flora Europ. Algarum, Sect. III. p. 9T. 



Sab. — In stagnis. United States. 



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

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

 cious ; male ^oenobium giving origin to numerous reddish spermatozoids (= Sphffirosphaera 

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

 fecundation, develop i^nto the same number of globose red oospores surrounded by a stellate 

 hyaline episporium. 



Bemarhs. — 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 aiforded no opportunity of studying their deve- 

 lopment a,nd life-higtory. 



Order Zy^ophycesB. 



Algse aut uni- aut pseudomulti-cellulares, sine vegetatione terminali et ramificatione vera. Cellulae 

 singulae aut geminatae aut seriatim conjunctse. Multiplicatio fit cellularum divisione in unam 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 DESMIDIACEiE. 



Algae unicellulares, sine ramificatione vel vegetatione terminali. Cellulfe forma admodum varia, 

 plernmque in medio plus minus profunde constrictse et in duas semicellulas symmetricas divisas! 



