Ser. Rhodosperme^. Fam. GdidiacecB. 



Plate XCIX. 

 ACROTYLUS AUSTRALIS, /. 4^. 



Gen. Char. Frond compressed, linear, dichotomous, composed of three 

 strata of cells ; the medidlary of branching, reticulately anastomo- 

 sing, slender filaments ; the intermediate of roundish-angular cells ; 

 the cortical of vertically seriated, coloured cellules. Fructification : 



1, conceptacles semi-immersed in the frond, opening by a terminal 

 pore, containing numerous parietal tufts of moniliform spore-threads ; 



2, zonate tetraspores, in spot-like, defined sori, under the apices of 

 the segments. — Acrotylus (/. Ag^, from a/c/jo9, topmost^ and TvXo^i, 

 a tumour or callus ; alluding to the apical sori. 



Trom compressa, linearis, dicJiotoma, dratisfere tribus contexta ; strata medtd- 

 lari ex fills elomjatis ramosis intertextis anastomosantibusque, intertnedio 

 celluUs rotundato-amjulatis, corticali cellulis minutis in fila moniliformia 

 verticalia subramosa ordlnatis formato. Fruct.: 1, desmiocarpia frondi semi- 

 immersa, carpostomio demum aperta, fascicules parietales plures filorurti spori- 

 ferorum fovetdia ; 3, tetraspores zonatim divisa, in sores definitos infra apices 

 seymentorum evolutos nidulantes. 



Acrotylus australis, J. Ag. 



Acrotylus australis, /. Ag. Act. Holm. Oefvers. 1849, p. 87. Harv. Alg. 

 Austr. Exsic. n. 330. Harv. in Hook. Ft. Tasm. v. 2. p. 317. 



Hab. At Sydney, New South Wales, Baron Gyllenstierna, fide J. Ag. 

 Mouth of the Glenelg River, South Australia, Br. Curdie. Abun- 

 dant at Port Pairy, W. H. H. ; also at Western Port, Victoria, 

 W. H. H. Tasmania, C. Stuart. 



Geogr, Distr. Southern and eastern shores of Australia. Tasmania. 



Descr. Root discoid. Fronds tufted, 3-6-8 inches long, and as much in the 

 expansion of the branches, compressed, everywhere preserving a nearly 

 uniform breadth of 1-1^ lines, either stipitate or branched from the base, 

 many times dichotomous, with wide, rounded axils, fastigiate ; the apices 

 either rounded or obsoletely bidentate or emarginate. The forking is tolerably 

 regular. The margin of the segments is either simple or furnished with 

 lateral, proliferous, simple or forked lobules, from i-1 inch long, spread- 

 ing horizontally. All the ramification is strictly distichous. The concepta- 

 cles are scattered along the branches ; they are slightly raised towards one 

 side, depressed in the centre, and finally pierced in the depressions ; the 

 cavity is spheroidal, and the walls are densely set with tufts of branching, 

 monihform spore-threads, which are afterwards resolved into spores. Tetra- 

 spores are borne in oval or subrotund, defined, slightly raised and wart-hke 

 sori (scarcely so prominent as to be called nemathecia), and are 3-4 times 



