80 LAMINARIACE^. iv. 



callus, erect, many times forked, fastigiate ; segments compressed above, patent? 

 with acute axils." J. Ag. Sp. Alg. vol. l,p. 171. Kiitz. Sp. Alg. p. 569- Ch. 

 Pacifica and Ch. Atlantica, J. Ag. Liebm. p. 7- (Tab. IV. C.) 



Hab. On the Pacific coast of the Mexican Republic, Liebman. (v. s. in Herb. 

 T. C. D.) 



Fronds many, from the same scutate base, 2-3 inches long, stipitate, soon forked, 

 and then repeatedly divided dichotomously, the forks being closer and closer 

 upwards ; equal in diameter throughout, subcylindrical below, compressed above, 

 ^¥ith acute apices. The axils of the forks are narrow and acute. Colour in a dried 

 state very dark, brownish. I have not seen perfect fructification. 



I have not been able on the specimens which I have had an opportunity of 

 examining, to make out the structure of the fructification with sufllcient accuracy 

 to authorize my introducing the cushions of spore-filaments into the plate. The 

 above description is therefore chiefly translated from Prof J. Agardh's account of 

 the genus. In aspect the plant resembles a very narrow Dictyota^ but its substance 

 is very much thicker, and a section under the microscope shows it to be composed 

 of a much gi'eater number of rows of cells. The surface cellules are very minute, 

 and the cells increase in length and breadth as they lie more towards the centre of 

 the flesh. 



Order III -LAMINAHIACE^. 



Laminariece, Grev. Alg. Brit., p. 24. J. Ag. Symb. p. 4. Sp. Alg. p. 121- 

 Endl. 3rd, Suppl. p. 26. Kiitz. Phyc. Gen. p. 344, a7id part of ChordecB, p. 333- 

 Sp. Alg. p. 573. Laminaridce, Lindl. Veg. Kingd. p. 22. 



Diagnosis. — Olive-coloured, inarticulate seaweeds, whose spores are superficial, 

 either forming indefinite, cloudlike patches, or covering the whole surface of the 

 frond. (Plants of large size, not much divided, usually stipitate, foliaceous.) 



Natural chabactee. — Root rarely a simple, undivided disc ; commonly much 

 branched, or only simple and disc-like when young. As the plant advances in 

 growth, new accessory holdfasts are formed toward the base of the stipe round the 

 primary one, and these, lengthening and branching, unite into a conical mass of 

 rootlets (or cables), which together make up the compound root. Fronds of an 

 olive-brown or an olive-green colour, mostly becoming darker on exposure to the 

 air, in some cases turning green in drying ; usually tough and leathery in substance, 



