Sub-class T. 



MELANOSPERME^ or FUCALES. 



Harv. in Mack. Fl. Hih. part iii. p. 167 (1836). Fucoide^, 

 J. Ag. Alg. Meclit. p. 24 (1842). Fucoide^. (in part), Ag. Si/st. 

 p. XXXV. (1824). Aplospore.e (in part), Decaisne, An. Sc. 

 Nat. vol. 17,;?. 305 (1842). Phyce^ (in part), E/tdl. Gen. PL 

 3rd Suppl. p. 19 (1843). Fdcace.e (in part), Lindl. Veg. 

 Kingd. p. 20 (1846). 



Diagnosis. — Plants of an olive- green or olive-brown co- 

 lour. Fructification raoncEcious or dioecious. Spores olive- 

 coloured, either external or contained, singly or in groups, 

 in proper conceptacles ; each spore enveloped in a transpa- 

 rent skin {perispore), simple, or finally separating into several 

 sporules. Antlieridia, or transparent cells filled with orange- 

 coloured vivacious corpuscles, moving by means of vibratile 

 cilia. Marine. 



The plants comprised under this head are exclusively ma- 

 rine, and are known from all other sea-weeds by their olive 

 or dark brown colour. In some few the colour of the living 

 plant is a very pale olive, verging to light green ; and some 

 others assume verdigris tints in decay or in the process of 

 drying : but as a general rule, it may be said, their colours 

 are rather on the brown than the green side of olive, and be- 

 come darker in drying, often changing to black. 



Though some of the larger kinds inhabit deep water, and 

 are never laid bare on the recess of the tide, by far the 

 greater number are found on tidal rocks, where they are ex- 

 posed to the influence of sun and air for some hours each 

 day. And this exposure seems necessary to their healthy 

 growth and full development, as is proved in the case of 

 some Fuci which are occasionally raised from deep water. 

 In such situations fruit is not produced, and the fronds 

 have a weak and attenuated habit. That these plants are 



