O r d e r I . COG CO PH YC EÆ .
Unicellular algæ. Cells either single, or many associated in
families, tegument involute or naked, destitute of branches or
terminal vegetation. Propagation by cell-division or zoogo-
nidia.
This order includes the two families Paltnellaceæ and ProtoGoccaceat,
with nnmoveable cells, to which is attached a third, the VolvocimecB, with
mobile cells. The two former correspond to the Chroococcacece amongst
the class Phycochromacece. Although thns removed, it would seem from
recent researches, that there is, in some sort, a relationship between the
Palmellaceoe and Protococcacece on the one hand, and the Chrooeoccaceæ
on the other.
We can only direct attention here to the papers by P. Richter, in
“ Hedwigia,’ (xix., 1880, p. 154) on Glceocystis and (xix. 1880, p. 169
and 191), on the “ genetic Connection of certain Unicellular Phycoch-
romaceoe,” of which abstracts were published in the “ Royal Microscopical
Journal.”*
The conclusions arrived at are in favour of a sort of polymorphism.
“ The lowest form of the Phycochromaceæ is the naked Aphanocapsa
condition, corresponding to Palmella among the Chlorophyllophyceæ.
Prom this naked or only slightly encysted condition is developed the
Qlceocapsa or Qloeocystis form with several gelatinous envelopes ; the
Chroococcus type, when the investment is altogether wanting, or, when
there is only a single vesicular envelope, the cænobinm types. The
Glæocapsa type is specially adapted for exposure to the air, and growth
upon a comparatively dry substratum ; the cænobium type is developed
in water ; the Chroococoevs type in water, or on a moist substratum in
the air. With this is connected the cylindrical form, a higher stage,
because it displays a differentiation in the direction of growth, and a
development towards the filiform condition. This is not always developed,
and may be distiugnished into stable and unstable forms ; the
latter may occur in two or three varieties, and may go through the
following successive conditions :—
1.—Stable Apharocapsa and Palmella,
2.—Aphanocapsa and Palmella which have attained to Glæocapsa,
Glæocystü, or cænobium type, but which always revert to the naked
solitary spherical form.
3.—Stable Glæocapsa, Glæocystis, Chroococcus, and cænobium forms,
without reversion ,
4
1
4.—Cylindrical forms, the generations of which pass through the
solitary spherical CAphanocapsa and Palmella) condition, as well as the
Glceocapsa and similar forms.
5.—Cylindrical forms, which pass through only the Glceoeapsa and
similar forms.
6.—Cylindrical forms the generations of which revert to the Aphano^
capsa and Palmella condition, while the Gloeocapsa or any similar form
is suppressed.
7.—Stable cylindrical forms CSyneehoeoccus).
No reference is made in the above to the passage of Glceoeapsa into
the encysted filiform conditions of Sirosiplion corresponding to Palmo-
dactylon and Rormospora among the ChlorophyllophyceEe.”
* Vol. I., Second Series, 1881, PP- 98 and 201.
F a m il y I. PALMBLLACEj® .
Unicellular algfc, in the broadest sense. Cells either solitary,
or more or less numerous, associated in families, vegetating by
cell-division, propagation by gonidia, which are produced from
the ultimate generation of cells. Gonidia, when free, ciliate
(usually with a pair of cilia) actively mobile.
Genus 1. E R EM O S P H a iR A . Be Bary. (1858.)
Cells single, rather large, swimming free, spherical, cell wall
firm, with a hyaline border. Cell contents {Gytioplasma) green,
granulose, sometimes containing green lamina disposed in a
radiate manner. Multiplication of the cytioplasm by division
into two or four (or more) sister cells, which escape by the
rupture of the cell-wall {Gytioderm.)
Eremosplieexa v ix id is . BeBy. Gonj.p. 56, t. viii./. 26, 27.
Cells globose, large, of a beautiful grass gveen.— Babh. A lg .
iii. p . 24.
Chlorosphcera Oliveri, Henfr. Trans. Mior. 8oc. vii. p. 25
(1859), pi. 3. Kirch. Alg . Schl. p. 115.
S iz e , •0043--0059 in. = - I l - 'I S mm. (B a b k ) , -1--12 mm.
{M .G .G .).
In boggy ditches.
“ The ordinary appearance of the plant is that of a large green globe,
like a large spore, lying free in the water, or often gathered in loose
groups upon decaying vegetable structures, such as leaves of Sphagnum
contained in the water. The globe is a single simple cell, with a thm
membranous coat surrounding a mass of usually green granular contents.
Each cell produces two, or more rarely, four new ones.
Cells in various conditions, all magnified 400 diameters.
Genus 2. PIEUROCOCCTJS. Meneg. (1842.)
Cells segregated, globose (or angular from mutual pressure),
with a central nucleus. Single or associated in small families
which are either globose or oubioal. Cell wall firm, often thick,
even, hyaline. Cell contents homogenous green, or oily red.
Multiplication of cells by division in alternate directions. P ro pagation
by gonidia in proper cells (Sporangia).
Plants aquatic, or aerial.
*Speciej green.
P le u to c o c c u s v u lg a r is . Meneg. Nost. 38, t. 5 ,/. 1.
Cells variable in size, simple, binate or quaternate, or as many
as 32 associated in families, aggregated in a crustaceous, powdery
brigbt-green and somewhat gelatinous (when moist) stratum.