Smith—Monograph of Scenedesmus . 
461 
These lateral ridges are not so prominent as in S. acuti- 
formis Schroder and S. brasiliensis Bohlin and frequently 
can be seen only in the polar region (Figs. 90, 91); neither 
do they appear at the same place on all the cells of the 
coenobe, the median cells being ridged in the center of the 
side and the terminal cells generally nearer the outer edge 
of the coenobe. Ridges cannot always be distinguished on 
all of the cells (Figs. 109, 110) but no coenobia were found 
in which there was not an indication of ridges on one or 
more cells. 
GEOGRAPHICAL DISTRIBUTION 
Germany (Heering und Homfeld, 1904; Schmidle, 1900A; Selk, 
1907; Volk, 1903, 1905). Austria-Hungary (Reinhardt, 1905). 
Samoa (Wille, 1913). Singapore (Bernard, 1909). Switzerland 
(Chodat, 1902). 
Var. Chodatii nov. var. (PI. XXX: Figs. 111-114.) 
Cellulis longioribus atque angustioribus. Dimens. cell. 
11 x 4, 12 x 3.5, 15 x 5 p. 
This variety was isolated but once, the material for the 
pure culture being collected on the Dane County Fair 
Grounds. The shape of the cells and the poles not being in 
lateral contact separate this from the foregoing. 
Var. subalternans nov. var. (PI. XXX: Figs. 115-120.) 
Longitudo cellularum 3-plo latitude; cellulis saepe pyri- 
formis; subalternis dispositis. Dimens. cell. 9x3, 9x4, 
11 x 5, 12 x 5.5 p. 
This is the only horn bearing strain isolated in which the 
subalternate arrangement of the cells in the coenobe is a 
constant character. Too much stress cannot be attached 
to this as a distinguishing characteristic; since occasional 
subalternating cell arrangements are found in many species. 
The pyriform character of the cells is much more pronounced 
in this variety than in the others of S. armatus. Certain 
colonies apparently have no lateral ridges (Figs. 119-120) 
but these instances are of very rare occurrence, while the 
horn on the pole of a median cell was found but once (Fig. 
119). 
