THE GREEN ALGAE OF NORTH AMERICA 99 



The specimens distributed by Miss Tilden consist of this 

 species in company with Protosiphqn botryoidcs (Kiitz.) Klebs. 

 Family 3. CHLOROTHECIACEAE- 



Unicellular, attached ; asexual reproduction by (uniciliate ?) 

 zoospores formed one or more in a cell ; sexual reproduction by 

 (uniciliate ?) gametes formed one or more in the vegetative cell, 

 or from cells developed in greater or less number within the 

 vegetative cell ; by union of these is formed a normal plant, 

 either directly or by means of another generation of zoospores. 

 In one genus there is a vegetative jdivision of the cells, the 

 daughter cells attached by gelatinous stalks in a tree-like colony. 

 Fresh water plants. Only one genus represented here. 

 CHARACIOPSIS Borzi, 1894, p. 151. 



Cells pyriform or ovoid, with several chromatophores, at- 

 tached ; erect or oblique, with longer or shorter stipe ; asexual 

 reproduction by uniciliate zoospores (possibly biciliate with one 

 cilium much reduced) formed many in a cell, developing directly 

 into a plant like the parent ; sexual reproduction by the forma- 

 tion of numerous cells, with membrane, each produ^ng 2-4 

 zoogametes, by whose conjugation is formed a resting'zygote, 

 ultimately developing into a plant like the parent. 



In habit the species of this genus closely resemble species of 

 C/iaracium, but possess a sexual reproduction, and have zo- 

 ospores with only one cilium or with merely the rudiment of a 

 second cilium. In Characium there is only one chromatophore ; 

 in Characiopsis several chromatophores in a cell. 



KEY TO THE SPECIES OF CHARACIOPSIS. 



i. Without basal disk. 2. 



i. With basal disk. 3. 



2. Cell ellipsoid with rounded summit. 3. C. ellipsoidea. 



2. Cell lanceolate with acute or apiculate summit. 2. C. minuta. 



3. Stipitate, outline broadly lanceolate or ovate. i. C. acuta. 



3. Sessile, outline narrowly lanceolate, acuminate, more or less oblique. 



4. C. subulata. 



1. C. ACUTA (A. Br.) Borzi, 1894, p. 153; Characium acutum 

 A. Braun, 1855, p. 41, PI. V. C.; Wolle, 1887, p. 177, PI. 

 CLIX, fig. 2. Cell 15-20X6-10 /*, erect, straight, broadly 

 lanceolate or ovate in outline, equally attenuate each way, sub- 

 acute, opening at the top ; stipe slender, 5-10 /* long, expanded 

 below into a brownish disk. Pa. Europe. 



2. C. MINUTA (A. Br.) Borzi, 1894, p. 152; Characium 

 minutiim A. Braun in Kiitziug, 1849, p. 892 ; 1855, p. 46, PI. 



