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



constricted, di- trichotomous ; branches strongly constricted at 

 the base, often clavately swollen at the end or when forking ; 

 lateral branches also common, usually short and simple, occa- 

 sionally opposite. In shallow water, in company with Bostrychia 

 tend/a (Vahl) J. Ag., Lvngbya confcrvoidcs Ag., etc. Marine. 

 \V. I. 



Nothing being known as to its reproduction, the inclusion of 

 this plant in Dichotomo siphon is only provisional ; in vegetative 

 characters the correspondence is marked. It forms rather dense 

 mats on the surface of the Bostrychia, and appears to be common 

 in Jamaica and other West India islands. The filaments in the 

 under part of the mats are colorless as in Vauchcria ; at first 

 glance one is reminded of the simpler forms of Udotca minima 

 Ernst, 1904, PI. VII, figs, i-io, but though part of the plant is 

 colorless, part bright green, there is no distinction in form 

 between the two as in the Udotca, and both seem to remain 

 prostrate. In a few instances there have been noticed short 

 simple branches in three or four opposite, approximate pairs, 

 with triangular outline, like the tip of a branch of Bryopsis 

 plnmosa, but this may have been accidental ; there was nothing 

 to indicate that it was a distinct erect growth. The constrictions 

 at the base of the branches are strongly marked, with stratified 

 thickening inside the wall ; the constrictions in the filaments 

 may be distant, or they may be scarcely more than one diameter 

 apart, when the frond appears markedly moniliform. 



The following species was omitted from the proper place, 

 p. 183 of this work. 



ULOTHRIX SCUTATA Jonsson, 1904, p. 57, figs. 8 and 9. 

 Filaments attached by a basal disk, with even or lobed margin ; 

 lower cells 5-6 /A diam., 1-3 diam. long; upper cells 9-16 p. diam., 

 ys-i diam. long; chromatophore zonate, not occupying the 

 whole length of the cell, with one pj-renoid. Filaments with 

 more or less distinct constrictions, at intervals of about 4 cells. 

 Greenland. 



The basal disk characteristic of this species is iisually sepa- 

 rated from the rest of the basal cell by a sharp constriction ; in 

 addition to the disk, the filaments are often attached by rhi- 

 zoids to the substratum, fronds of 



