430 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



145 /j., not quite filling the oogonitim ; ripe oospore with occa- 

 sional brown spots, and thick, minutely pitted membrane ; 

 antheridium straight with rounded apex, at the end of the branch 

 bearing the oogonium, single, or oftener tw r o, 30-40 //, diam., 

 separated from the branch by an empty cell ; with one apical 

 tube. Greenland. Northern Europe. 



18. V. LITOREA Agardh, 1821, p. 463; Nordstedt, 1879, p. 

 1 80, PI. II, figs. 1-6; Farlovv, 1881, p. 105; P. B.-A., No. 166. 

 Marine, dioecious; filaments 70-95 //, diam.; antheridium at the 

 end of a longer or shorter branch, supported by an empty cell, 

 cylindrical, rather obtuse, with 2-4 short, lateral projections ; 

 oogonium at the extremity of a reflexed branch, clavate or 

 obovoid, about 200 /u, wide and 300-400 /j. long ; separated from 

 the filament by a short, empty cell; oospore subglobose, with 

 thick membrane,. 1 80- 250 /A diam., occupying the upper part of 

 the oogonium. Mass, to N. J. Jtnrope. 



A coarse, dingy plant, with long filaments forming loose tufts, 

 on mud and gravel at low water mark.* 



DICHOTOMOSIPHON Ernst, 1902, p. 115. 



Frond filamentous, inarticulate, multinucleate, with disk- 

 shaped chromatophores without pyrenoid ; filaments di-poly- 

 chotomous, attached below by slender, colorless rhizoids ; 

 branches constricted at base to about half the diameter ; similar 

 constrictions formed at intervals between the branchings ; mem- 

 brane thickened at the constrictions, often becoming brown ; 

 starch accumulation in large quantities throughout the frond. 

 Sexual reproduction by terminal oogonia and antheridia ; 

 oospore globose, with triple membrane, germinating after a 

 resting period. Asexual reproduction by akinetes, in the form 

 of tubercular swellings at the ends of the branches, or oftener 

 on special lateral branches, germinating after a resting period. 



This genus differs from Vaiichcria by the true dichotomous 

 branching, the peculiar asexual reproduction, the corymbose 

 arrangement of the sexual organs, the presence of starch in 

 large quantity, and the tendency to articulation shown by the 

 constrictions. While the sexual fructification, except as to the 

 position of the organs, is the same as in Vaiichcria, the vegetative 

 characters are curiously like those of some of the marine 

 Codiaceae ; when a Udotea, for instance, is decalcified, the fila- 



*V. velutina Wolle, 1887, p. 153, is given merely from older references. 

 According to Farlow, 1881, p. 105, a specimen from J. W. Bailey, marked 

 by him V. velutina, is probably V. Thuretii Woronin. 



