IV. 



DICTYOTACE.E. 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 Kutzing 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.-DICTYOTACE^. 



Dktyotea^, Gr^. Alg. Brit. p. 46. /. Ag. Sp. Alg , vol. \,p. 68. Endl^d. SuppL, 

 p. 24. Dlctyotece, Encceliece, and part of Chordece and Phycosendece, Kidz., 1 hyc. 

 Gen. pp. 337, 336, 333, 296. Dictyotidw, 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.) 



Natueal Chahactee. Root usually a minute membranous disc or holdfast ; 

 sometimes a conical fleshy mass of large size, densely clothed with curled wool-like 

 iointed 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 *^«Onler is distinguished^^ 

 In some, these internal cells form a regular honey-combed tissue ?f ^^^l^^'^^f^;^ 

 cells • but in others they are cylindrical, arranged in longitudmal series or filament^s 

 wWci, 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 formexl of numerous cells 



Lcentrically disposed round an imperfectly hollow axis, /hen we have bag-lA^e 

 simple fronds, as in Asperococcus, formed as it were by the mflation of such a 



