334 Mr. J. Ralfs on the Nostochineae. 



The turgid sporangia and large, compressed vesicular cells 

 characterise the species. 



Plate VIII. fig. 11. a, immature state; b, mature state. 



6. S. Mooreana ( ). Ordinary joints subspherical ; vesicular cells 



barrel-shaped, much narrower than the large broadly-elliptic spo- 

 rangia. 



Ireland, Mr. Moore, to whom I am indebted for specimens. 



Ordinary cells minute, somewhat orbicular. Sporangia very 

 turgid, often nearly orbicular, much larger than either the vesi- 

 cular or the ordinary cells. Vesicular cells minute, smooth and 

 barrel-shaped. 



I regret that I have only seen imperfect and dried filaments of 

 this species intermixed with Nostoc variegatum, Moore ; in a re- 

 cent state therefore the form of the ordinary cells may not agree 

 with the above description, still the large turgid sporangia must 

 distinguish it from every species but Sphcerozyga Berkeley 'ana , 

 and from that it differs in its vesicular cells, which are compara- 

 tively much smaller and also longer than broad. 



Plate VIII. fig. 12. Mature filament. 



*** Dissepiments obscure, cells longer than broad. 



7. S. leptosperma (Kiitzing). Filaments elongated, not constricted 

 at the dissepiments ; ordinary joints longer than broad, confluent ; 

 vesicular cells elliptic ; sporangia linear. Cylindrospermum lepto- 

 spermum, Kutzing, Bot. Zeit. 1847, p. 198; Species Algarum, 

 p. 294 ; Tabulae Phycologicse, t. 99. fig. 11. 



Ditches and pools. Near Carnarvon and near Barmouth, J. R. 

 France, Lenormand. 



Sphcerozyga leptosperma occurs in large, shapeless, gelatinous 

 masses in still waters. Its colour varies from deep green to pale 

 yellowish green, but when the filaments are comparatively few it is 

 nearly colourless. The ordinary joints are longer than broad, sepa- 

 rated only by transverse dissepiments, which are not contracted, 

 and indeed are often so obscure, that, in the recent state, they 

 can hardly be detected, whilst the filaments, in all respects but 

 their enlarged cells, appear not unlike those of an Oscillatoria. 

 Vesicular cells at first barrel- shaped, finally elliptic, and as broad 

 as the sporangia, the early state of which they somewhat resemble, 

 but they may be recognized by the absence of granular contents 

 and by their globules. Sporangia cylindrical, four to six times 

 longer than broad, truncate, slightly broader than the ordinary 

 cells. 



The confluent ordinary cells with their obscure dissepiments 

 distinguish Sphcerozyga leptosperma from every other British 

 species. 



Plate VIII. fig. 13. Mature filament. 



