418 ANNALS OF THE MISSOURI BOTANICAL OARDBN 



[Tol. 10 



Family Chaetophoracbab 

 Genus chaetophora Schrank 



Chaetophora elegans (Roth) Ag. 



Crow Lake. 



Genus stigeoclonium Ktitz. 



Stigeoclonium sp. 

 Eastgate's Pond. 



PI. 21, figs. 14-16. 



The alga was a small epiphyte growing in great abundance on 

 Cladophora sp., which was often entirely covered for lengths of 

 3 or 4 segments with its closely packed filaments (pi. 21, fig. 14). 

 A number of epiphytic species of Stigeoclonium have previously 

 been described, but the alga in question does not seem to agree 

 with any one of them. 



The thallus consists of two distinct parts — a basal portion of 

 compact branching filaments, forming an almost parenchy- 

 matous stratum firmly applied to the wall of the Cladophora, 

 and an upright system of usually short crowded branches. The 

 upright branches are not usually more than 2 or 3 cells in length 

 and rarely branch, but if branched may often give rise to long 

 piliferous hairs (pi. 21, figs. 15, 16). These hairs show a cellular 

 structure and are very abundant, being often developed in addi- 

 tion directly from the creeping portion of the thallus. Many of 

 the cells in the erect filaments were very swollen, and their 

 contents showed cleavage in preparation for the development of 

 zoogonidia. 



Of the previously known species of Stigeoclonium, the forms 

 nearest to the North Dakota examples are the following: — St. 

 farctum Berth, in Nova Acta Acad. Caes. Leop. 40: 201. pi. 16, 

 f. 1-5. 1878; St. proslratum Fritsch in Ann. S. Afr. Mus. 9: 531. 

 1918; Stigeoclonium sp. Mobius in Hedwigia 26: 238. pi. 0, f. S. 

 From St. farctum Berth, our alga differs in the shorter length 

 of its erect filaments, which were rarely longer than 3 cells, 

 whilst in Berthold's form they were 4-7. St. prostratum Fritsch 

 differs in the somewhat laxer development of the basal portion of 

 the thallus, and also in the fact that an upright system of branches 

 is only present in certain regions, where the basal part of the 



