Smith—Monograph of Scenedesmus. 
451 
(Lemmermann, 1908A). Sweden (Lemmermann, 1904A; de Toni 
and Forti, 1899A). 
AFRICA. Lake Tanganyika (G. S. West, 1907). 
AMERICAS. Paraguay (Lemmermann, 1910A). United States 
Var. platydisca, nov. var. (PI. XXX: Figs. 101-105.) 
Cellulae coenobium saepe 8, in seriam duas in uno piano, 
foramina inter cellulas parva. Dimens. cell. 8x 4.5, 8x5, 
9x5.5, 10x5.5, 11x6 y. 
The form which I have isolated in pure culture has been 
figured by Nageli, West, and others as one of the normal 
variations of S. bijuga (Turp) Lag. However, since the cell 
arrangement shows a greater resemblance to S. arcuatus 
than to S. bijuga , this form is placed as a variety of S. 
arcuatus. 
All the colonies in a culture have the cells arranged in the 
characteristic flat surface, thereby differing from the typical 
form. The interstices between the cells are much smaller 
and angular by compression, where the cells come in con¬ 
tact with one another. 
The normal number of cells in a colony is eight (Figs. 
101, 103-105) although four-celled coenobia have been 
found (Fig. 102). These, however, cannot be distinguished 
from thp four-celled colonies of S. arcuatus except by the 
size of the individual cells, which average five microns 
shorter and two microns narrower than those of S. arcuatus. 
This variety may have been described by Chodat as the 
variety disciformis of S. bijuga but his description “Cellules 
en petite thalle, 4-ou octocellulaire, polyhedrique par com¬ 
pression” is indefinite in that it may refer to the form under 
consideration or to S. bijuga var. irregularis (Wille). 
11. S. producto-capitatus Schmula. (PI. XXV: Fig. 11.) 
Schmula, 1910, p. 85; Figs. 1-5. Brunnthaler, 1913, pp. 170, 
172; Fig. 27. Chodat, 1913, p. 25. 
“Cellulae singulae, aut in coloniis, quae duas tresve aut 
quator cellulas continent. Cellulae visae ab adversa parte 
(fronte) 11-14 y longae, in media parte 3-3.5 y latae, hinc 
ad extrema versus instar capitis dilatatae, productae et 
rotundatae sine aculus, praeditae membrane tenuissima, 
nucleo centralo et duobus pyrenoidibus. Cellulae a vertice 
rotundae et diametro 3-3.5 y. A latere visae cellulae prae- 
