millimeters to 15 centimeters in height; composed of axial strands 

 of long cells which give rise on all sides to dense fascicles of out- 

 ward-directed branches, usually curved. Apical cells of branches 

 sharp-pointed or setiferous. Cells of main axis 10-15/x in diameter; 

 as much as 10 times the diameter in length in the axial filaments. 



This is a variable species, occurring mostly in hard water habitats, 

 although it is found in acid lakes and swamps. In swiftly flowing 

 streams the plant may be very long luxuriantly-developed green 

 strands. In lakes it is commonly found forming crinkly, tuberculose 

 or short arbuscular growths on Typha and Scirpus, as well as on sub- 

 merged wood. In very hard water the thalli are often lime-encrusted 

 and pale green. Some expressions have been given varietal names, 

 but the forms are so intergrading and seem to be so definitely related 

 to enviionmental conditions that it is not possible to separate them. 

 The rather firm mucilage of this species is one of the habitats of 

 Chaetonema irregulare Nowak., which is easily overlooked among 

 the dense branches of the host. 



Common. Attached to stones and wood, mostly in flowing water, 

 but frequently on the culms of rushes in shallow water of lakes. 

 Mich., Wis. 



Chaetophora pisiformis (Roth) C. A. Agardh 1812, p. 43 



PI. 13, Figs. 2, 3 



Plants attached, in the form of either distinct or confluent globules 

 of firm mucilage, in which dichotomously branched filaments radiate 

 from a common center, ending anteriorly in fascicles of branches. 

 Apical cells sharply pointed, rarely setiferous. Cells of the main axis 

 about 7/x in diameter, 15-35fi long; cells of the branches only slightly 

 narrower and shorter. 



On submerged substrates, mostly in cold water streams and lakes; 

 swamps. Mich., Wis. 



DRAPARNALDIA Bory 1808a, p. 399 

 Thallus consisting of an axis of larger barrel-shaped or cylindrical 

 cells attached to a substi'ate by rhizoidal branches and giving rise 

 to alternate, opposite, or whorled fascicles of smaller-celled branches, 

 which terminate in bluntly pointed or setiferous cells. Plants em- 

 bedded in copious, soft mucilage. Chloroplast a parietal band in the 

 cells of the main axis, a laminate plate covering the entire wall 

 (or nearly so) in the smaller cells of the branches; pyrenoids 1 to 

 several. 



Because the species of this genus seem to prefer cold water hab- 

 itats they frequently are collected during the spring months. In early 



[119] 



