MARINE ALGA! OF BEAUFORT, N. C. 497 
cc. Polysiphonous axis plainly evident, thallus composed of one or more circles of large 
cells around a row of central cells, apical cell brapaycepedy or ebhaeehs divided, 
tetrasporangia produced from pericentral cells............. elcisiee 
d. Thallus with conspicuous erect branches fromis a eeopiins» ‘on8e7 weligtteNouily 
branched, pericentral cells with secondary transverse divisions. . .5- Bostrychia (p. 506). 
dd. Thallus erect throughout, radially branched, pericentral cells wibiort second- 
arpitransverse divisions Wester) phils. SIS AISLE RIGO. Setia LGR 22s . ete @ 
e. Trichoblasts persistent, covering portions of the frond in the form of colored, 
branched, monosiphonous filaments. . : He ..4. Brongniartella (p. 505). 
ee. Trichoblasts evanescent, occurring aie on ‘the. younger ‘woniend of the frond...,.... fe 
jf. Thallus with dense parenchymatous structure, polysiphonous arrangement not 
conspicuous, covered by a dense cortex, pericarp thick, tetrasporangia occur- 
ring singly without conspicuous order in spindle-shaped branchlets markedly 
constricted at their bases......... 35 .2. Chondria (p. 498). 
Jf. Thallus with rather loose itenactsney sinokysigtomond extameeniente cotispicuctia, 
naked or covered by a thin cortex, pericarp thin, tetrasporangia usually 
occurring singly in straight or spiral rows in scarcely altered branchlets. 
ASIF silel tad Pare eeies Vie Tb MaRnabiae wl Fan. was o<nes 3. Polysiphonia (p. 502). 
Genus 1. Laurencia Lamouroux. 
Laurencia, Lamouroux, 1813, p. 130. 
Frond erect, terete or flattened, richly radially or distichously branched; structure 
cellular, dense, cells large within, becoming smaller toward the surface, situated without 
conspicuous order, central row of cells not evident except toward apices, apical cell 
surrounded by evanescent trichoblasts, sunk in a depression, somewhat tetrahedrally 
divided, pericentral cells not formed; tetrasporangia scattered over the ultimate, fre- 
quently shortened branchlets among the outer subcortical cells, with no apparent rela- 
tion to pericentral cells, triangularly divided; antheridia oval to oblong, borne on tufts 
of branched filaments (trichoblasts) arising from the bases of open, scutellate, apical 
depressions; procarps borne on trichoblasts within the apical depressions, coming sec- 
ondarily to lie on the surface as a result of later growth, cystocarps scattered over the 
smaller branches, prominent, ovate to spherical, pericarp thick, opening by an apical 
pore, gonimoblast composed of branched filaments radiating from a basal placenta, 
bearing single pear-shaped carpospores in their terminal segments. 
About 50 species, often with ill-defined limits and exceedingly difficult to determine, 
in warm seas. 
Laurencia tuberculosa J. Agardh. 
Laurencia tuberculosa, J. Agardh, 1852, p. 760. 
Laurencia tuberculosa, Harvey, 1853, Pp. 75. 
Laurencia gemmifera var. 8B, Harvey, 1853, D. 73- 
Laurencia tuderculosa, De Toni, 1903, p. Sor. 
A. A. B. Ex. No. 62. 
P. B.-A. Nos. 439, 1937- 
Frond subterete or slightly flattened, about 1 to 2 mm. wide, 5 to zo cm. tall, branching alternate 
subdistichous, pinnately decompound, branches spreading, bearing numerous short, simple, blunt, wart- 
like tubercular branchlets distichously arranged below, naked toward the apices; tetrasporangia in the 
short, tubercular branchlets; texture rather cartilaginous; color crimson to fleshy purple. 
Florida and West Indies. 
