Smith—Monograph of Scenedesmus. 
467 
number of horns. Figure 136 shows an instance in which 
one cell has three spines while the other has four. Although 
there is always one spine at the end of the pole, the position 
of which corresponds to that of S. quadricauda , there are 
frequently one or two more (Figs. 139, 133). 
Correlated with the presence of numerous spines on the 
terminal cells is that of spines on the poles of the median 
cells. The number and position of these median polar 
spines is even more variable than is the case with the mar¬ 
ginal terminal spines. There may be one or more on each 
pole of all median cells (Fig. 135); or one pole may possess 
one or more spines and the other none (Fig. 139). An ex¬ 
treme development of this condition is the presence of only 
one spine on the median cells of the coenobe. (Fig. 136). 
GEOGRAPHICAL DISTRIBUTION 
EUROPE. Austria-Hungary. (Gutwinski, 1890; Hansgirg, 
1886, 1905; Pascher, 1903; Riabinine, 1889A, 1889B). England 
(Fritsch, 1906; Hassall, 1845; Ralfs, 1845, 1846, 1848; G. S. West, 
1899; West and West, 1897B, 1901B, 1909B). Germany (Kaiser, 
1908; Kirchner, 1878; Lemmermann, 1893; Marsson, 1901A; 
Schmidle, 1900A; Schroder, 1897C; Schorler, Thallwitz und Schiller, 
1906; Selk, 1907; Volk, 1903, 1905). Ireland (W. West, 1892A; 
West and West, 1902B). Italy (Gugliemetti, 1910). Roumania 
(Teodoresco, 1907). Russia (Dorogoslaisky, 1904; Gutwinski, 
1891). Scotland (West and West, 1901, 1905, 1909B). Sweden 
(Borge, 1907A, 1913; Lagerheim, 1883; Petersen, 1911). Switzer¬ 
land (Chodat, 1902, 1913; Huber, 1905). 
AFRICA. Madagascar (West and West, 1895). 
ASIA. Ceylon (West and West, 1901A). 
AMERICAS. Argentina (Borge, 1907B). Brazil (Bohlin, 
1897). Canada (Klugh, 1911). United States (Buchanan, 1907; 
Collins, 1909; Conn and Webster, 1908; Fink, 1905; Snow, 1903; 
Wolle, 1887). 
Var. longicauda nov. var. (PI. XXX: Figs. 121-125.) 
Dimens. cell. 7x3, 7 x 3.5, 8x4, 9x6 y. Long. acul. 
10-6 y. 
In this variety the spines are not as abundant as on the 
typical form, three to four being the usual number for the 
terminal cells, while rarely more than one is found at each 
pole of the median cells. 
