PROTOCOCCACE, 33 
accenobium. Propagation by division in the cells whence arise 
gonidia, which unite themselves into a ccenobium within the 
mother-cell, and are at length set free by the rupture of the 
cell-membrane. 
Genus 25. SCENEDESMUS. Meyen. (1829.) 
Cells polymorphous, equal or unequal at the ends, often pro- 
duced into a spine-like horn. Frond or family composed of 
from 2 to 8 oblong, fusiform, or elliptic cells, connected into a 
single or double continuous row; propagating by means of the 
repeated segmentation, in parallel planes, in one or two direc- - 
tions, of each of the cell- contents into one or more brood families 
(not motile), set free by the bursting of the parent-cell wall. 
Nageli. 
A. Cells unarmed. 
Scenedesmus obtusus. Meyen. Rabh. Alg. 111., 63. 
Cells oblong or ovate, obtuse at the poles, 4-6-8 loosely con- 
nected in a simple series, or joined obliquely, 3-5 times as long 
as broad. 
Size. Cells :0055-:007 mm. diam. 
Ralfs Ann. Nat. Hist. xv., p. 404, t. 12, f.8. Brit. Desm. 
p. 193, t. 81, f.16. Archer in Pritch. Infus. p. 753, t. 1, f. 
37-39. Hass. Alg. p. 394, t. 92, £15. 
In boggy pools. 
This species appears to be much less common than §. quadricauda, 
from all forms of which it may be readily distinguished, not only by the 
difference in the form of the cells and absence of spines, but the remote- 
ness of one cell from its neighbour and their alternation. 
Plate XIII. fig. 5. Cells in families of 4 and 8, magnified 400 
diameters. 
Scenedesmus acutus. Meyen. Rabh. Alg. 111., 68. 
Cells fusiform or ovate-fusiform, acute at each extremity, 
2-4-6-8 united in a series, either single and straight, or double 
and irregularly alternate ; 3-6 times as long as broad. 
Sizz. Cells 0035-0055 mm. diam. 
Ralfs Ann. Nat. Hist. xv., p. 404, t. 12, f.6. Brit. Desm. 
193, t. 81, f. 14. Hass. Alg. 893, t. 92, f. 14. 
In pools and boggy places. 
var. b. obliquus. Rabh. Alg. 111., 63. 
Cells elliptic, fusiform, arranged in two generally oblique 
series, the outer cell of each not in contact with any of those in 
the other series. 
Scenedesmus obliquus, Ralfs Desm. p. 192, t. 81, f. 15. 
English Botany, t. 29338. 
Scenedesmus triseriatus, Ralfs Ann. Nat. Hist. xv., p. 408, t. 
12, f. 7. 
