SIPHONACE^. 9 



Okder I.— SIPHONACE^. 



Siphonece and Caulerpece, Grev. Alg. Brit. p. 183. J. Ag. Alg. Medit. p. 17- 

 Endl. 3rd Suppl. p. 16. Dne. Class, p. 32 ; (also Halymedece, Dne.) Lindl. Veg. 

 Kingd. p. 18, and Vaucheriew, in part, p. 22. Vaucheriece, Caulerpece, Codiece (in 

 part), Kiltz. Sp. Alg. pp. 486, 494, 500. 



Diagnosis. Green, marine or fresh water Algae, naked or coated with carbonate of 

 lime, composed either of a single, filiform, branching cell, or of many such cells united 

 together into a spongelike frond. 



Natural Character. Root, where it is developed, formed of many branching 

 fibres interwoven together and entangled ; sometimes penetrating deeply into the sand 

 in which the plant grows, and attaching itself to the separate grains of sand, which 

 serve further to consolidate the mass of fibres. Frond very variable in appearance, 

 and differing much in complexity of structure, but always formed of very long, 

 branching, inarticulate filaments, which arise from the continued groAvth and evolution 

 of a single, undivided cell. In the genera of simplest structure, such as Bryopsis 

 and Vaucheria, the frond consists of a single branching filamentous cell, with a thin, 

 membranous, hyaline cell-wall ; its cavity being filled with a granular semifluid colour- 

 ing matter or endochrome, which may be wholly discharged if the tube be wounded 

 and slightly pressed. In Bryopsis the unicellular fronds stand apart from each other, 

 though many often rise nearly from the same base. In Vaucheria several such fronds 

 are interwoven together at the base, but remain distinct in their upper branches. In 

 Chlorodesmis there is a further union of many such threads, whose lower portion 

 unite together to form an evident stipes or trunk, which is crowned with a pencil of 

 free filaments ; the whole frond resembling a little tree. This habit, however, is not 

 so obvious in the American species as it is in Ch. comosa, the first described species of 

 the genus. Again, in Codium, we find a structure essentially the same as in Vau- 

 cheria and Chlorodesmis, but the union of the filaments is still more intimate. To 

 the naked eye, the species of Codium resemble green sponges or pieces of green cloth 

 or velvet, having a perfectly definite outline and closely interwoven substance, and it is 

 only when we tear or cut them asunder under the microscope that we perceive their 

 true structure. We then find that all the central part of the substance of the frond is 

 composed of innumerable interwoven, longitudinal branching cells, and that the velvetty 

 pile which constitutes the surface is formed of the tips of excurrent branches of the 

 axial cells, lying close together and presenting only their extremities to the eye. In all 



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