19G CRYPTO NEMIACE^. v. 



swell into spindle-shaped, pod-like receptacles, which, when mature, dropoff, leaving 

 the branches truncated. In these receptacles either nuclei or tetmsj)ores are lodged ; 

 the former sunk among the cells of the intermediate layer, from some of whicli 

 they are evolved ; the latter lying among those of the outer stratum. Colour dark 

 red-brown, blackish when dry. Substance fleshy, sub-coriaceous when dry. 



XX. ACROTYLUS. J. Ag. 



Frond terete or compressed, cartilaginous, simple or dichotomous, consisting of 

 two strata ; the medullary stratum of slender, elongate, branching and anastomosing 

 longitudinal filaments ; the cortical nan"ow, of minute, roundish, densely packed, 

 coloured cellules, vertically seriated. FaveUce (known only in one species) formed 

 in wart-like swelhngs round the apices, many together, containing within a hyaline 

 periderm numerous angular spores. Tetraspores (known only in one species) 

 formed in definitely circumscribed spot-like sori (nemathecia) situated below the 

 apices of the segments, elongate, surrounded by slender filaments, zonate. 



A small genus founded by Prof. J. Agardh on an East Indian and an Australian 

 species, to the former of which the plant now to be described is closely related. 

 A. 2)rl!imatlcus, J. Ag. is described as being prismatically three-or- four-angled, a 

 character which it certainly possesses when dry ; but I am of opinion that in the 

 recent state it is cylindrical, like our A. clavatus, which, if dried without pressure, 

 also collapses in a prismatic-angular manner, and equally refuses to recover its 

 shape on being moistened after having being dried. 



1. AcROTYLUS clavatus ; frond, from a filiform stipe, club-shaped, terete, obtuse, 

 simple or forked (the branches being then club-shaped,) proliferous from the apex. 



Hab. Thrown up from deep water, Key West, W.H.H. (63). (v. v.) 



Boot a small disc. Stq?es a quarter to half an inch high, as thick as hog's bristle, 

 filiform, ending in an incrassated collar. Frond springing from the centre of the 

 collar, about two inches long, club-shaped, tapering to the base, incrassated and ob- 

 tuse at the apex, terete, prismatically shrinking when dried without pressure, and 

 not recovering its form on re-moistening, simple or forked. Colour^ a very dark 

 purplish-red. Substance firmly cartilaginous. Structure very dense. Fruit un- 

 known. 



Of this curious plant I collected a very few specimens at Key West, in February, 



