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



rapidly between these points that it forms an arch. Wolle's 

 figure is unsatisfactory, giving no idea of the form of the cells or 

 of the setae, and not showing the manner in which the filaments 

 encircle the host. 



Family 8. COL,EOCHAETACEAE. 



Frond consisting of dichotomously branched, monosiphonous 

 filaments ; all prostrate on the substratum, or with erect 

 branches, branches distinct or laterally united to form a disk, 

 or a pulvinate mass ; growth by division of terminal cells only ; 

 cells uninucleate, with a parietal chromatophore, covering 

 nearly all the cell wall and one pyrenoid, often producing 

 slender, sheathed setae ; asexual reproduction by biciliate zo- 

 ospores without stigma, produced one in a cell, escaping by an 

 opening in the wall, and germinating directly ; sexual repro- 

 duction by oogonia and antheridia, produced in some species 

 on the same individual, in some species on separate individuals ; 

 autheridia formed by the division of vegetative cells, or by 

 outgrowths from them, producing each one spherical, biciliate 

 spermatozoid, released by the dissolving of the cell wall ; 

 oogonium formed of the terminal cell of a branch, which en- 

 larges and at the same time sends out a tubular prolonga- 

 tion ; after fertilization by the spermatozoid this is closed 

 by a partition at its base, branches in some species grow- 

 ing out from the cell below the oogonium or the neighboring 

 ce'lls, and forming a more or less complete cellular coating to it, 

 becoming red or red-brown. The oospore with its coating rests 

 for a long period, then the spore divides and increases in size, 

 breaking through and throwing off more or less completely the 

 coating, and from each'cell is produced a zoospore, which ger- 

 minates and produces the ordinary plant. Only one genus. 



COLEOCHAETE Brebisson, 1844, p. 29. 

 Characters of the Family. 



This genus represents the highest type of fructification among 

 the green algae, showing a considerable likeness to some of the 

 lower forms of mosses, and possibly also an approach to some of 

 the Florideae. The fronds of the various species form small, 

 bright green disks or cushions on fresh water plants or other 

 submerged objects. 



KEY TO THE SPECIES OF COLEOCHAETE. 



i. Forming gelatinous cushion-like masses. 6. 



i. Forming monostromatic expansions. 2. 



2. Filaments more or less distinctly radiate. ?. 



2. Filaments spreading irregularly. 



