132 FRESH-WATER ALG^E OF THE UNITED STATES. 



Plate CXIV, figs. 6, 7, parts of two sterile filaments from 

 living plants; figs. 8, 9, part of a fertile filament from 

 Wittrock's Monograph. 



Subsection D. ULOTRICHIN^:. 



Simple, unbranched filaments. Earely with short, lateral, 

 rhizome-like branchlets ; zoospores of two kinds ; maerozoo- 

 spores with four ciliae which do not copulate ; microzoospores 

 with two ciliae of which eight or more are developed in a cell ; 

 these may copulate, but without it they propagate the species 

 vegetatively. Two microzoospores copulating produce a fertil- 

 ized macrozoospore, which gradually develops a plant. Besting 

 spores have not been observed. 



Kirch ner remarks, "filaments of plants of this section 

 often divide, or break up irregularly; the chlorophylous 

 granules of the contents enlarge, the cell walls break and 

 decay and then the cell contents are dispersed and often pro- 

 duce large colonies of spherical unicellular forms similar to 

 Palmetto, or Protococcus. 



Inasmuch as the UtotricMnce forms develop from macro- 

 zoospores and from microzoospores they are not always 

 quite uniform in size or appearance. 



Some of the species enumerated below are of questionable 

 value. 



Genus HOEMISCIA, (Fr.) Aresch. 



(Hormotrichum, Kg. Hormospora, Breb.) 



Three names which have been applied, and which con- 

 tinue in use by some algologists, to represent a class of 

 plants embracing a number of forms more or less nearly 

 allied, possessing an outer investment of colorless mucus. 

 Cienkowski and other modern observers consider them mere 

 stages of growth, or perhaps rather, stages of decay. In 

 illustration of some of the differentiations common to some of 

 the Ulotrichinae compare some of the following references. 



Plate CXX, figs. 21-30 ; Conferva floccosa, first the vegeta- 

 tive condition (figs. 21-25) ; next, may be termed a sporan- 

 gial condition (figs. 26-27 ) and lastly (figs. 29-30 ) a true 

 Hormistidj or Hormospom form. These and intermediate 

 conditions are often traceable in the same plant. Turning to 

 Plate CXXI, figs. 6, 7, and 10, 11, we have Conferva vul- 



