295 



ALG.E GLOBULIFERvE. 



FAM. XVI. ULVACEJE. 



Char. Frond gelatinous, saccate, tubulose, or membranaceous. 

 Cells either spherical and scattered singly throughout the 

 mucous frond irregularly, in pairs, in fours, or multiples 

 of that number ; or polygonal, and crowded together. 



THE species of the family Ulvacece appear, so far as the 

 freshwater examples are concerned, to require a separation 

 into two sections : the first including the genera Ulva, at least 

 the single freshwater species of that genus Ulva bullosa (of 

 the marine species, I have no exact knowledge), Tetraspora, 

 Hydrurus, and Merismopedia ; the second, the genus Entero- 

 morpha. In the first, the cells are small, and spherical, being 

 imbedded at considerable intervals from each other in the 

 mucous frond ; in the second, the cells are large, polygonal, 

 and attached firmly to each other, the mucous nidus having 

 disappeared. 



The reproduction of this family does not appear to have 

 been satisfactorily determined. In Agardh's memoir on the 

 propagation of the Algce, referred to so often, the following 

 remarks occur : 



" My father advanced the opinion that the cellules disposed 

 often in fours were the seeds, which was contradicted by 

 Lyngbye. Greville in the work cited above * observes, that 

 from three to four granules are disposed in the cellules of the 

 frond, but he pronounces not upon the function which ought 

 to be attribute^ to these granules. In this uncertainty, some 

 observations on the movement of the globules of Tetraspora 

 lubrica, should easily decide the question ; but no person 



* Algae Britannicae. 



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