PROTOCOCCACE. 45 
Pediastrum rotula. (Zhr.) Br. Unicell. Aly. p. 101. 
Ceenobium orbicular or oblong, size and number of cells 
variable, 4-8-16-32, pierced with openings, bright green, even ; 
cells of the periphery truncate at the base, more or less dilated 
upwards, deeply bifid, sinus acute, lobes straight, narrow, biden- 
tate, teeth erect or divergent, somewhat bent; cells of the 
centre variable in form, usually polygonal, repand, or notched, 
containing a single paler spot, sometimes not visible, 
Rabh. Alg. iii. p. 79. 
Pediastrum heptactis, Hassall Alg. t. 92, f. 9. 
Pediastrum incisum, Hassall Alg. t. 92, f. 8. 
In pools, &c., throughout Europe. 
Plate XVII. fig. 2. b, marginal cell; a, 4-celled coonobium; c, 
6-celled coonobium; d, 8-celled coonobium; e, /, h, 16-celled coonobium ; 
g, irregular coenobium, 
Sub-Family 8. SorastRez. 
Cells polygonal, often shortly horned, associated in a hollow, 
spherical or cubical ccenobium ; cell-membrane thin;  cell- 
contents green, homogeneous, then granular; chlorophyllose 
vesicle central or sublateral. Propagation by gonidia, in two 
modes in the same species (simultaneous, or after division), 
united into a cenobium within the mother-cell, escaping by 
rupture of the membrane.—Rabh. Alg. Eur. iii. 79. 
Genus 30. CHLASTRUM. Wig. (1849.) 
Ceenobium globose, hollow within, formed of a single stratum 
of cells, reticutately pierced.—Rabh. Alg. Eur. iii, 79. 
Frond, or family, hollow, globular, or subcubical, composed of poly- 
gonal or spherical cells, united in oue layer into a hollow clathrate net- 
like family, the cells drawn out on the exterior into one or more lobes, 
or simply spherical; propagating by the segmentation of the cell-con- 
tents into a definite number of portions which become arranged into a 
hollow young frond, resembling the parent, ultimately set free by the 
bursting of the parent cell.—Pritch. 755. 
Celastrum sphericum. Wig. Hin. Alg. 97. 
Ceenobium globose or subglobose, composed of 4-8-16 or a 
larger number of cells, perforated, areola 3-4-5-6 angled ; cells 
rounded, by mutual pressure angular, outer angles somewhat 
conical, obtusely rounded at the apex ; interstices 5-6 angled. 
Sizz. Ccenobinm ‘04-085 mm. diam.; cells 021-023 mm. 
Celastrum Naegelii, Rabh. Alg. iii. 79. Archer in Pritch. 
Infus. p. 755, t. 1, f. 49-55. 
In boggy places. 
Plate XIX. fig. 2. a, 6, families magnified 400 diameters; ¢, cell 
magnified 800; d, cell of C. cubicum, with two obtuse processes ; e, cell 
of Ca@lastrum, perhaps C. cambricum, with one obtuse process. 
H 
