— 108 — 



the formpreviously recorded from Barton's pond as S. Hassallii 

 (Jenn.), Petit (Fritsch and Ricli, 1907), is nothing else than 

 this two-spiralled i'orm of S. quadrata. 



III. — Oedogonium Pringsheimii, Tram., forma. The 

 détermination of this speeies lias caused us nmcli trouble owing 

 to the very variable shape of the oogonia. The prévalent shape 

 was more or less that of a pear (fig. 1, B), the aperture of the 

 oogonium being at the broader end; in the same filament how- 

 ever otlier oogonia were observed, which were almost complète! y 

 spherical, and there were ail transitions between thèse two 

 shapes. The aperture was in nearly ail cases completely supe- 

 rior. The oospores almost completely filled the oogonia. The 

 dimensions were : diam. fil. 5-7 y-, 3-4 times as long; diam. 

 oogon. 20-21 y-, long. 25 y-. No maie filaments were observed. 



The form observed cornes near to that described as var. 

 varians by Nordstedt (winch Hirn [Mcmogr. d. Oedogonia. 

 ceen, 1900, p. 172] regards as a form of var. Nordstedtii, 

 Wittr.), but diflers in its smaller dimensions. We hâve exper- 

 ienced much difficulty in determining the met'iod of opening of 

 the oogonium. Oedogonîum Pingsheimii is an operculate 

 form, but Wittrock M remarks : operculo apertis, rima angus- 

 tissitna et perindistincta ». We hâve observed oogonia with an 

 undoubted operculum, but in most cases it was very difficult to 

 regard the opening as anything else than a pore. 



IV. — Oedogonium multisporum, Wood (fig. 1, A). A 

 speeies of Oedogonium occurred in 1907 and 1908 and in espe- 

 cially large quantity in 1910, which appeàrs to bethe 0. multi- 

 sporum of Wood (cf. Hirn, loc. cit., pp. 232, 233 and tab. 

 XXXIX, fig. 239). A far as we are aware this speeies lias only 

 been hitherto recorded from ditches near Philadelphia. As 

 Wood's original diagnosis was not very salisfactory, we give 

 the following emended diagnosis : 



• < ii'. dioicum, nannandrium; oogoniis plerumque singulis vel 

 interdum 2-3-seriatis, suboviformibus vel subglobosis, poro 

 supramediano (interdum fere superiore) apertis; oosporis globo- 

 sis, oogonia fere explentibus, membrana laevi ; cellulis sufful- 

 tioriis eadem forma ac cellulis vegetativis ceteris ; nannandribus 

 paullum curvatis vel fere rectis, propevel in oogonia sedentibus, 

 antheridio exteriore, 1-3 vel 4-cellulari. 



(1) Prodromus monographiœ Oedogoniearwm, 1874, p. 33. 



