MARINE ALG OF BEAUFORT, N. C. 427 
Genus 2. Rhizoclonium Kuetzing. 
Rhizoclonium, Kuetzing, 1843, p. 261. 
Filaments usually prostrate, consisting of a single series of multinucleate cells, with 
net-shaped chromatophore and several pyrenoids, unbranched or, in some species, with a 
few irregular branches similar to the axis, and with more or less numerous rhizoidal 
branches, which are mostly unicellular, but sometimes consist of several cells. Asexual 
propagation by biciliate zoospores, with stigma, escaping through an opening in the cell 
wall; also by akinetes; but in only a few species has either form of fructification been 
found. 
About 25 species, in fresh or salt water or on moist earth, throughout the world. 
The filaments resemble those of Chatomorpha, but are less uniformly cylindrical, 
there being almost always more or less irregularity in the form of the cells. The short 
rhizoidal branches, when present, clearly characterize the genus, but they are not always 
developed, and when they are absent, the resemblance to Chetomorpha is deceptive. 
Rhizoclonium riparium (Roth) Harvey. Fig. 3. 
Conferva riparia, Roth, 1806, p. 216. 
Rhizoclonium riparium, Harvey, 1849, pl. 238. 
Rhizoclonium riparium, Harvey, 1858, p. 92. 
Rhizoclonium riparium, Farlow, 1882, p. 49, pl. 3, f. a. 
Rhizoclonium riparium, De Toni, 1889, p. 278. 
Rhizoclonium riparium, Collins, 1909, p. 327. 
A. A. B. Ex. No. 213. 
P. B.-A. Nos. 24, 1734 (266,976, var. implerum; 1688, var. validum). 
Filaments usually pale green, forming expansions on ground or rocks in the littoral zone; cells, 
usually 20 to 25 mic. in diameter, rarely a little more or less, length 1 to 2 diameters; branches none or 
few or many. 
Greenland to Florida; Alaska to Washington; California; South America; Europe; Borneo. 
Fairly abundant on rocks of Shackleford jetty, Beaufort, N. C., April, r908. 
Three varieties are recognized, depending on the amount and nature of the branching; there is no 
typical form distinct from these. 
It was not observed here in May, 1907, and has not been found in winter or summer. 
Genus 3. Cladophora Kuetzing. 
Cladophora, Kuetzing, 1843, p. 262. 
Frond composed of filaments of a single series of cells, the filaments branching, 
usually abundantly; branching lateral, but often coming to appear dichotomous: in 
consequence of the pushing aside of the original filament by the branch; attached at 
first, later attached or free floating; growth chiefly by division of the apical cell, subse- 
quent division of cells being exceptional; branches all of the same type; cells multi- 
nucleate, the chromatophore either covering the cell wall or forming a network on it or 
broken into numerous small disks; pyrenoids several in a cell; asexual propagation by 
four-ciliate zoospores; sexual reproduction by similar biciliate gametes, uniting and 
germinating immediately, or sometimes germinating without copulation; portions. of 
filaments sometimes capable of passing into resting condition, forming structures per- 
haps to be considered as akinetes. 
Three hundred to 400 species described, many of them on insufficient characters, 
occurring in fresh and salt water throughout the world. 
110307°—21——28 
