TETRASPORA. 301 



the attention which they require. I do not feel at all cer- 

 tain that either this species, or Tet. gelatinosa are really dis- 

 tinct from Ulva bullosa : at all events, it is certain that in 

 Ulva bullosa in its young state the frond is saccate or tubular, 

 and the granules arranged in fours : neither can any difference 

 be detected in the size of the cells in these supposed species : 

 all which circumstances lead to the suspicion that they are 

 but states of the same production. If the observation of 

 Vaucher be correct that the granules or cells undergo an in- 

 crease of size at the period of the complete developement of the 

 frond, and just before it passes to decay, then it would seem 

 that no certain character can be derived from their size, unless 

 the condition of the species as to age be likewise ascertained. 

 The frond of T. lubrica is stated to be larger than in the 

 following species, less gelatinous, with a more distinct mem- 

 brane and of a deeper colour. The tube finally ruptures, and 

 becomes membranaceous, with an irregular outline. 



2. TETKASPORA GELATINOSA Desv. 

 Char. Frond ovate, inflated, and very gelatinous. 

 Hook. Br. Fl. p. 313. ; Harv. in Manual, p. 176. 

 Hob. In freshwater streams attached to aquatic plants ; 

 Newcross, Killarney : W. H. Harvey. Botanic Garden, 

 Belfast : Dr. Drummond. Malahide : Mr. Moore. 



" Frond exceedingly lubricous and gelatinous, but firm, 

 delicately waved, and plaited, of an oval outline. Sporules 

 bright green, or arranged in fours or scattered." Harv. 



3. TETRASPOKA FLAVA Hass. 

 Plate LXXVIII. Fig. 11. 



Char. Frond when dried yellowish. Cells very minute. 

 Hob. Rocky rivulet, co. Antrim : Mr. Moore. 



This species at all events would appear to be distinct, the 

 cells being two or three times smaller than those of the two 

 preceding TetrasportB. 



