Smith—Monograph of Scenedesmus. 453 
S. hystrix forma denticulatus. Volk, 1905, p. 65. Selk, 1907, 
pp. 7, 57, 68, 79, 85, 94, 99, 108, 115 r 
S. hystrix forma denticulatus genuinus. Selk, 1907, p. 68. 
“Sc.cellulis quaternis, ovatis vel ovali-oblongis, cruciatim 
dispositis vel subalternantibus, utroque polo rotundatis et 
denticulus parvis, plerumque binis, instructis. Membrana 
cellularum subcrassa. Dimens. cell. 7x5, 10x7, 12x6, 
13x9, 15x9, 15x11 p” 
Although this species occurs abundantly in this vicinity 
it has never been isolated in pure culture. For this reason 
the variations in the size of the cells cannot be given; so the 
existence of the variety zig-zag , described by Lagerheim, 
’where the cells are about half as wide as the typical form, 
cannot be affirmed or denied. Another even more important 
point is whether or not the arrangement of the cells in a 
linear series or an alternating series is a constant character, 
or if the alternating type of colony gives rise to the linear 
type or vice-versa. G. S. West (1904B) shows a linear type 
of colony in which two daughter colonies are being liberated 
that have the alternating arrangement of the cells, a condi¬ 
tion which corresponds with my observation made on 
material from the field. Until this question of cell arrange¬ 
ment has been definitely settled by cultural studies, it seems 
best to follow the general practice of recognizing both alter¬ 
nating and linear types as distinct. 
GEOGRAPHICAL DISTRIBUTION 
EUROPE. Austria-Hungary (Gutwinski, 1897A, 1897B; Hans- 
girg, 1886, 1889, 1890A, 1891, 1892B, 1905; Pascher, 1903; 
Ruttner, 1906). Belgium (de Wildemann, 1888). Denmark 
(Chodat, 1900). England (Griffith, 1912; W. West, 1892B; West 
and West, 1897B, 1901B). Germany (Heering und Homfeld, 1904; 
Kirchner, 1885; Lemmermann, 1893, 1898A, 1899, 1901B, 1905B, 
1905G, 1906,1907B, 1908E; Marsson, 1911; Migula, 1907; Schmidle, 
1897; Schorler, Thallwitz und Schiller, 1906; Schroder, 1896, 
1897A, 1897B, 1897C, 1899; Schroter, 1884; Selk, 1907; Voigt, 
1902; Volk, 1903, 1905). Ireland (Adams, 1908; W. West, 1892A; 
West and West, 1902B). Italy (Forti, 1902; Garbini, 1899A; 
Gugliemetti, 1910). Scotland (West and West, 1905). Sweden 
(Borge, 1895, 1907A; Lagerheim, 1883; Petersen, 1911). Switzer¬ 
land (Chodat, 1902; Dalla Torre und von Sarnthein, 1901; Huber, 
1905). 
