296 ULVACEJC. 



having "as yet observed the act itself of their disjunction 

 from the membrane, it has not been ascertained whether it 

 was the cells themselves or that which they contain which 

 escaped from it. That which is certain is, that the sporules 

 of this plant are not more naked (an opinion advanced by 

 ]\I. Gaillon) than those of any other Ulvacece. 



" The Ulvacece properly so called are composed of cells some- 

 times arranged in a single layer, which constitutes an elongated 

 tube entirely empty, sometimes disposed in two layers, com- 

 pressed the one against the other, and forming a flat mem- 

 brane more or less extensive. Their sporules are lodged in 

 these cells, and issuing by a pore situated on the surface, they 

 offer the same phenomenon of locomotion which we have seen 

 to belong to the preceding families. 



" Their movement is more slow and in the cellules straighter 

 than amongst the Confervea. Their beak is not so pointed, 

 and is not near so well separated from the body ; but never- 

 theless it is always the thinnest end of the oviform bodies 

 which is foremost during the movement. The sporules are 

 five or six in number in each cellule ; in some of them there 

 were two or three which were much smaller than the others, 

 a difference which is also observed in the ConfervecB, but in a 

 manner less apparent. 



" Finally, it is only in the Ulva clathrata that I have ob- 

 served the complete developement of these sporules. The ger- 

 mination (if one may so name a phenomenon analogous to that 

 act in more perfect plants) consists in this species of a longi- 

 tudinal expansion, during which the green matter insensibly 

 transforms itself into transverse bands. In this state one 

 might easily take the young plant for a species of Conferva, 

 but soon the bands being divided longitudinally, and so become 

 disposed in two series, one cannot longer mistake it." 



Section i. 

 Granules simjjly imbedded in the frond. 



39. ULVA Linn. 

 Char. Frond gelatinous, saccate or membranaceous. Cells 



