Mr. J. Ralfs on the Nostochineae. 331 



on one side and apparently an ordinary cell on the other, but 

 this occurs only when the sporangia begin to be developed, and 

 the individual on one side is more forward than that on the 

 other. In such a case close examination will detect a slight pre- 

 liminary elongation of the incipient sporangium. The sporangia 

 indeed are always developed, first on one side of the vesicular 

 cell and then on the other, and whatever number may occur 

 together they follow the same rule, and are produced alternately 

 adjacent to those previously formed, and as they are thus pro- 

 duced in succession they all vary in size (except in the mature 

 plant), the inner ones in each group being the largest. 



Sphcerozyga differs from Trichormus and Dolichospermum by 

 producing its sporangia adjacent to the vesicular cells ; its fila- 

 ments also are straighter, and its sporangia more elongated than 

 in the former genus. The interstitial position of the sporangia 

 and vesicular cells distinguishes it from Cylindrospermum, and 

 the ordinary cells are not disciform as in Spermosira. 



* Filaments moniliform ; sporangia elongated, not turgid. 



1. S. Carmichaelii (Harvey). Filaments moniliform, with tapering 

 extremities ; ordinary joints distinct, subquadrate ; sporangia ob- 

 long ; vesicular cells spherical. Belonia torulosa, Carmichael, 

 Alg. Appin ined. ; Harvey in Hooker's Brit. Flora, vol. ii. p. 379 

 (1833) ; Manual of Brit. Algae, p. 167. Sphterozyga compacta, 

 Kiitzing, Phycologia Generalis, p. 211 (1843); Phycologia Ger- 

 manica, p. 1 72. Anabcena marina, De Brebisson in Ann. Sc. Nat. ! ; 

 Kiitzing, Species Algarum, p. 287 ; Tabulae Phycologicae, t. 92. 

 fig. 111. Sphcerozyga Carmichaelii, Harvey, Phycologia Britan- 

 nica, t. 1 13 A (1847) ; Kiitzing, Species Algarum, p. 294 ; Tabulae 

 Phycol. t. 99. fig. 4. 



/S. tenuissima ( ). Filaments very slender. 



On the damp soil in salt-marshes flooded at spring tides, more 

 rarely in brackish ditches or upon decaying marine algae. Appin, 

 Capt. Carmichael. Anglesea ; Barmouth ; Penman Pool near Dol- 

 gelley ; Braunton near Barnstaple ; Penzance, J. R. Shirehampton 

 near Bristol, Mr. Thwaites. 



fi. Shirehampton, Mr. Thwaites. 

 France, Brebisson ; Germany, Kiitzing. 



Stratum tender, very thin, of a dark or bluish green colour 

 when recent, but opake and glaucous when dry. Filaments short, 

 straight, slender, moniliform, with attenuated ends. Ordinary 

 joints distinct, the terminal ones longer than broad and trian- 

 gular or conical, the others nearly equal in length and breadth, 

 at first quadrate, finally rounded at their angles, and when dried 

 orbicular. Whilst dividing they are geminate and longer than 

 broad. Vesicular cells orbicular or oval and generally ciliated. 



