24 
THE SEAWEEDS 
which he himself had figured seven forms in his “Phycologia Britannica> 
all of them described previously by authors as distinct species. They are all 
very delicate tubular plants, with many elongated branches, mostly pale 
green in colour. 
Family CLADOPHORACEAE. 
The thallus is a single row of cells, simple or branched, each cell multinu- 
cleate, the nuclei minute. The chlorophore lines the wall of the cell but 
is often broken up. The cell wall is firm, sometimes lamellose. Repro- 
duction takes place by means of tetraciliate zoospores and by the union of 
biciliate gametes, just as in Ulvaceae, with confervaceous habit. 
Sub-Family CLADOPHOREAE. 
Thallus simple or branched, filamentous, articulated, branches separated 
by a septum from the cell from which they arise. 
a. Filaments of the thallus quite simple Chaetomorpha. 
aa. Filaments freely branched Cladophora. 
aaa. Filaments sparingly provided with short, mostly 
un jointed hook-like branchlets Rhizoclonium. 
Fig. 6 . — Chaetomorpha Darwinii. 
Fig. 7 . — Chaetomorpha aerea. 
