Sub-Family 2 . Ohloeoooooaoeæ.
Cells sphæroid, either single and free, furnished with a
chlorophyllose vesicle and a pale lateral spot, sometimes with an
ample tegument, or more often accumulated in strata or little
clusters. Propagation by zoospores, formed by division of the
cell contents, escaping by rupture of the cell wall.
G en u s 23. CKLOROCOCCUBI. Fries. (1825.)
Cells subglobose, single or in clusters. Characters the same
as the sub-family.
A. Species green.
t Tegument thin.
Chlorococcum h um ico lum . {HägJ Baih. Kr. FI. Sachs, 137.
Stratum effused, dark-green, pulverulent ; cells globose,
variable in size, often many united in families, involved in a
common hyaline tegument ; cell membrane thin, but thickening
with age ; contents at first pale or yellowish-green, homogenous,
at length dark-green, granular.
S i z e . Cells -017 mm. diam., or less.
Eabh. Alg. iii. 58.
Cystococcus humicola, Nag. Einz. Alg. 85, t. 3, f. E.
On the naked ground (A. W. Wills').
Plate X I I . fig. 5. Cells and family maguified 400 diameters.
Chlorococcum fru stu lo sum . (Carm) Bahh. Alg. iii.,50.
_ Thallus effused, pulverulent, green ; cells globose, of medium
size, associated in families which are involved in a broad hyaline
homogenous envelope.
S i z e . Cells -007 mm. diam. ; families t o -04 mm. diam.
Hcematococcus frustulosus, Hass. Alg. 380, t. 81, f. 1. Eng.
FI. V., p. 395. Harv. Man. 181.
Palmella frustulosa, Carm. MSS.
On moist rooks.
“ I t occurs in the form of a greyish black, fragmentary scnrf. On the
slightest pressure it separates into corpuscles of various forms, but
mostly sphærical, hyaline nnder the microscope, surrounded by a membranous
envelope, and including several granules.”—Oarm.
Plate XII. fig. 2. Families magnified 400 diameters.
Chlorococcum m uro ium . (Grev.) Balh. Alg. in ., 61.
Thallus crustaceous, yellowish-green ; cells subglobose or
oblong, with a rather thick hyaline mucous envelope ; cell contents
æruginoiis-green, homogenous.
S i z e . C e lls , in c lu d in g e n v e lo p e , -O lf i-’OS x ‘0 1 m m .
Grev. So. Crypt. FL, t. 325.
Hcematococcus murorum, Hass. 328, t. 81, f. 4.
On walls.
We have retained this in its present position in deference to Rabenhorst,
to whom the species must have been known. At the same time
its æruginous green colour seems to indicate an affinity with Fhycochro-
mophycece rather than the present order.
“ Plant producing spots on walls and stones of a yellowish green colour,
and at first very small, but afterwards indefinitely larger, from a number
becoming confluent. First discovered in this country by the Rev. M. J.
Berkeley on the freestone walls of Christ College, Cambridge.”—
Greville.
Plate X II . fig. 4i. Cells magnified 400 diameters. Some undergoing
division.
f t Tegument thick.
Chlorococcum g ig a s . Grun. in Rahh. Alg., No. 1436.
Stratum thin, green, mucous ; cells globose, large, either
single or associated in small families, always involved in a broad,
distinctly lamellose hyaline tegument.
S i z e . Cells •012--017 mm. diam. without the hyaline membrane.
Frotococcus gigas, Kutz. Phy. Gen. p. 145.
In pools, on walls and glass windows.
One of the finest species in this genus, and possibly not unoonmion.
We have met with it two or three times, but not in any great quantity.
I t must not be confounded with Glæocystis ampla.
Plate XII. fig. 3. Cells magnified 400 diameters, h, in different stages
of division.
B. Species red, rusty, or orange.
No British species in this section recorded.
Sub-Family 3 . P o l t e d r ieæ .
Cells single, segregate, free swimming, compressed, 3-4-8
angled ; angles more or less produced, sometimes radially elongated,
either entire or bifid, mostly armed, oblong-elliptic when
viewed laterally, rounded or rather truncate at the ends. Cell-
membrane th in , even. Chlorophyll-mass mostly granular,
equally distributed through the cell, sometimes with 1-4 reddish
oil-drops. Propagation unknown.
G e n u s 24. POLYEDRIUM. Niig. (1849.)
Characters the same as above for the sub-family.
A. Angles entire.
P oly edr ium g ig a s. Wittr. Sotvattensalger, p. 33, t. 4, /. 4.
Cells irregularly pentahedrical (rarely hexahedrical), angles
obtuse, sides concave.
S i z e . Maximum diameter of cells -065--075 mm. ; minimum
diameter -035-'045 mm.
Archer, in Quart. Journ. Mior. Science xvii. (1877), p. 105.
In standing pools.
This large and distinot species has the angles rounded and unarmeA
Plate XIII. fig. 1. a, b, o, cells in three positions, magnified 400,
a fte r Wittrock.