94 
Blackman and Tans ley, 
38. Eremospliaera. De Bary, 1858. 
Cells single, spherical, unusually large, floating freely, 
Chloroplasts numerous, containing pyrenoids. 
39. Exceiitvosfrhaera. Moore, 190T. 
Cells single, large, spherical to elliptical or irregular. 
Chloroplasts numerous, angular, closely covering the 
wall, each containing several miuute pyrenoids. 
Reproduction by numerous aplanospores, which escape 
by dissolution of part of the mother-wall. 
40. Oocyst is. Nageli, 1855. 
Cells oval, one to eight enclosed in a firm mother-cell 
wall. Colony floats freely. Chloroplasts many, 
parietal. 
41. Chlorella. Beyerinck. 1890. 
Cells spherical or slightly elliptical, minute, with a thin 
wall and a single parietal chloroplast, usually 
possessing a distinct pyrenoid. 
[An alga occurring under very various conditions and frequently 
symbiotic.] 
42. Polyedrium. Nageli, 1849. 
Cells of very irregular and variable polyhedral shapes, 
with spines and other outgrowths. The daughter- 
cells are at first invested with mucilage, but afterwards 
float freely. Chloroplast single, with a pyrenoid. 
§ Cells tending to form linear aggregates. 
43. Catena. Chodat, 1900. 
Cells cylindrical, with flat ends, and joined in chains of 
usually four cells by the centres of the ends. 
44. Gloeotila. Kiitzing, 1843. 
Cells cylindrical, connected up into short filaments, with 
slight constrictions between the cells. 
45. Stichococcus. Nageli, 1849. 
Cells cylindrical, existing either freely or united to form 
an unconstricted filament of some solidarity. 
(C.) PLANT-BODY NON-MOTILC during the dominant phase, mostly ooenocytic, 
NOT MULTIPLYING BY VEGETATIVE DIVISION. 
[In this section are included all those forms of the non-motile 
Protococcoideae in the life-history of which new cells arise only from 
swarmers and never by the septation of existing vegetative cells. 
The majority of genera are single cells or coenocytes, bnt in a few 
the plant-body consists of a coenobium of coenocytes. arising by the 
apposition of a number of zoospores. 
In most of the forms which have been carefully investigated the 
single nucleus of the original cell has been found to divide during the 
growth of the cell till a considerable number is present, and the plant- 
body becomes a simple coenocyte. 
It seems clear that it is from this section of the Protococcoideae 
that the more complex coenocytic types of the Siphonales have been 
evolved.] 
