54 SEA MOSSES. 



well to paper, and is, by far, the most beautiful and 

 most manageable of our UIvce, for the herbarium. 



Ulva lactuca,* L. 



The full grown plant differs from the polymorphus 

 laiissinia, which it in most respects, much resembles, 

 chiefly in these two particulars. It is of a paler color, 

 and a much thinner substance. On dissection, it is 

 found to consist of but one layer of cells, while U. 

 lattissima has two layers. This fact, no doubt, accounts 

 for both the peculiarities named above. When young, 

 it is said to form an inflated bag like an overgrown 

 Enteromorpha intestinalis, then at length by splitting 

 along the side, floats out a thin membrane of but 

 one layer of cells. It is an annual, and appears 

 in spring and summer along with, but not so com- 

 mon as U. lattissima. I found it in August, very 

 plentiful and very large at Southold, L. I. 



Ulva fasciata, t Delile. 



The frond is more rigid even than that of U. 

 lattissima; rises from a short stem, and is divided into 

 several strap-shaped segments half to three-fourths of 

 an inch wide, of nearly equal breadth throughout, and six 



* Lactuca == lettuce, 

 t Fasciata == bundled. 



