MARINE ALGM 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 Chaetomorpha, but are less uniformly cylindrical, 

 there being almost always more or less irregularity in the fotm 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 Chaetomorpha is deceptive. 



Rhizoclonium riparium (Roth) Harvey. Fig. 3. 



Conferva riparia. Roth, 1806, p. 216. 



iparium, Harvey, 1849, pi. 238. 

 iparium, Harvey, 1858, p. 92. 



Rhizoclonium 

 Rhizoclonium 

 Rhizoclonium 



iparium, Farlow, 1882, p. 49, pi. 3, f. 

 iparium, De Toni, 1889, p. 278. 

 iparium, Collins, 1909, p. 327. 



A. A. B. Ex. No. 213. 



P. B.-A. Nos. 24, 1734 (266,976, var. implexum; 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 i 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, 1908. 



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. 



