ULVACEiE. 
51 
Hab. Key West, W.H.IL, Prof. Tuomey. (No. 103). (v. v.) 
Fronds at first globose, like tubers, heaped together, hollow and empty or filled with 
sea-water, attached to the rock and to each other by a few short, rooting processes ; at 
length irregularly torn, and then forming expanded, cartilaginous, or skinlike coarsely 
reticulated membranes. The membrane is wholly composed of a single layer of large, 
globose, or by mutual compression hexagonal cells, which closely cohere by their sides, 
leaving the convex ends of the cell free, and these form the surface of the membrane, 
which when dry resembles a piece of fish skin, or a miniature honeycomb. When the 
cells have been separated, each is seen to be marked at the line of junction by a double 
row of circular discs. In full grown cells the primordial utricle is easily separable from 
the outer cell-wall, and contains a green, granular endochrome ; from which, by cell- 
division, four new cells are formed, and thus the frond extends by repeated quadrisection 
of its component cells. The cell-wall is very tough and semifibrous in texture, more 
like an animal than a vegetable membrane ; and I have seen hairlike processes issue 
from it internally, analogous perhaps to the fibrous processes of the membrane of Caulerpa. 
I cannot say whether this be a constant character. It was observed in specimens from 
the Pacific brought home in spirit, and cannot be readily ascertained from dried specimens. 
Plate XLIY. B. Fig. 1 . Dictyospilzeria favulosa , the natural size. Fig. 2. Portion 
of the surface, showing the division of the cells. Fig. 3. One of the cells of which the 
frond is composed, removed ; the latter figures magnified. 
Order IV.— ULVACE^E. 
Grev. Alg. Brit. p. 168. Hook. Br. FI. 2, p. 309- Haw. Man. p. 211. J. Ag. 
Alg. Medit. p. 14. Endl. 3rd Suppl. p. 18. TJlvacece et Enter omorphece, Kiitz. 
Spec. Alg. pp. 471-475. 
Diagnosis. Green or purple, marine or fresh water Algse, composed of small, poly- 
gonal or quadrate cells, forming expanded membranes or membranous sacs or tubes ; 
rarely arranged in filaments. Fructification , zoospores formed in the cells of the frond. 
Natural character. Root a small disc, or point of attachment. Frond formed of 
small, often very minute, roundish, quadrate or polygonal cellules cohering together 
into thin, filmy membranes, of no very definite form, and either expanded into broad 
leaves, contracted into narrow ribbons, or forming tubes which are either simple or 
branched. In those of lowest organization, such as Tetraspora , the frond is of a nature 
so loosely gelatinous that it can only by courtesy be called a membrane, and the cells 
which give it consistency are widely separated by transparent jelly. In Prasiola the 
