IV. 
DICTYOTACEiE. 
99 
filaments. These are only found in their full development on mature specimens. 
Colour a brownish or greenish olive. Substance membranaceous and soft. 
In habit this plant has more resemblance to Asperococcus echinatus than to the 
preceding species, but the structure of the walls is more in accordance with Chorda. 
There is also considerable affinity with the Antarctic Adenocystis , a little group 
that scarcely differs essentially from Chorda , with which Kiitzing unites it. I 
cannot agree so well with that author in making C. lomentaria merely a variety of 
C.filum , from which it has latterly been kept separate by most authors, and from 
which it differs in many essential characters. 
Order IY -DICTYOTACEiE. 
Dictyotece , Grev. Alg. Brit. p. 46. J. Ay. Sp. Alg , vol. I, p. 68. Endl. 3d. Supply 
p. 24. Dictyotece , Encoeliece , and, part of Chordece and Phycoseridece , Kiitz ., Pliyc. 
Gen. pp. 337, 336, 333, 296. Dictyotidce , Lindl. Veg. Kingd p. 22. 
Diagnosis. Olive-coloured, inarticulate seaweeds, whose spores are superficial, 
and disposed in definite spots or lines ( sori ). ( Frondose , or rarely filiform plants of 
small or mediocre size , and membranaceous texture ; their surface reticulated with large 
cells.) 
Natural Character. Root usually a minute membranous disc or holdfast ; 
sometimes a conical fleshy mass of large size, densely clothed with curled, wool-like 
jointed hairs. Fronds of an olive-green or olive-brown colour, mostly becoming 
paler on exposure to the air ; of a membranaceous, flexible substance, rarely lea- 
thery or cartilaginous, and scarcely at all juicy : composed of two or more strata 
of cells, of which the inner ones are largest, usually empty, and either quadrate or 
appear so in profile. These large cells, seen through the smaller superficial and 
coloured cells which form the actual coating of the frond, give to its surface, when 
examined under a lens of moderate power, a netted appearance which is highly 
characteristic, and has suggested the name by which the Order is distinguished. 
In some, these internal cells form a regular honey-combed tissue of twelve-sided 
cells ; but in others they are cylindrical, arranged in longitudinal series or filaments 
which, however, cohere closely throughout their length, forming a membrane, and 
are not separable without laceration. 
In external habit the plants of this Order exhibit considerable variety. In some 
of the humblest, the frond is an unbranched thread formed of numerous cells 
concentrically disposed round an imperfectly hollow axis. Then we have bag-like, 
simple fronds, as in Asperococcus , formed as it were by the inflation of such a 
o 2 
