118 FRESH-WATER ALG.E OF THE UNITED STATES. 



CHAETOPHORA MONILIFERA, Kg. 



Thallus subglobose, scarcely 2 mm in diameter, dull olive 

 or reddish ; filaments dichotomous, largely colorless, 

 branches radiately disposed, more or less moniliform ; arti- 

 culations elliptical globose; (probably developing zoospores), 

 extremities acute or rounded, not hair -like. 

 Pools, swampy places, Pennsylvania. 



Plate CIII, fig. 19, natural size of thallus ; fig. 18, small 

 part of thallus magnified 250 diameters. 



CHAETOPHORA LONGIPILA, Kg. 



Thalli very small, about the size of Poppy seed, orbicular, 

 green, smooth ; filaments fasciculately branched, apices pro- 

 duced into a long, articulate, colorless hair-point. 



Often abundant on old culms of Sagittaria and other plants 

 in mill ponds. 



This plant appears to be perfectly developed, and there is 

 much uniformity in size, yet I have questioned whether 

 it may not be a young, or dwarfed form. 



Plate CIII, figs. 16, 17, the thalli ; natural size, and one 

 magnified. Filaments without gelatinous sheaths. Rhizomes 

 none. 



Genus 19, MICROTHAMNION, Naeg. 



Articulate filaments dichotomously or trichotomously branched; 

 now and then very much branched, straight, with the terminal 

 cell primarily linear, obtuse ; later swollen, forming a sporan- 

 gium. Cell contents effused, containing scattered amylaceous 

 granules. A peculiar mode of branching has been observed, at 

 least in one species ; in the development of a new branch the 

 lower of two cells grows out or turns to one side ; the branch 

 does not start at the point of bending but a little above, where 

 the joint is formed; ultimate joints obtuse. 

 Propagation by zoospores. 



MlCROTHAMNION KUETZINGIANUM, 



Vegetative green; branches somewhat dichotomously 

 spreading ; basal cells colorless, attached, ends obtuse ; arti- 

 culations cylindrical, usually somewhat geuiculate near 

 the upper ends ; 3-6 times as long as wide. 



Diameter, 4-6 yu. 



Ponds, water troughs, floating or attached. 

 Plate CV, figs. 1-4, four parts of plants with sporangia. 



