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Genus 80. C H IO R O C H Y T R IU B I. Cohn.
P lan t endophytic; green, nnicellular ; cells globose, or somewhat
irregnlarly hi-, tri-, or multi-lobed ; densely filled with
chlorophyll, first dividing into large segments, and then these
giving origin to innumerable pyriform zoospores, which escape
through a tubular process.
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C h lo io c h y tx inm L emnse. Oohn. Beitr. I., 87.
The zoospores, impinging on the epidermis of the duckweed
a t the junction of two cells, after germination commences a tube
is produced, which, entering between the walls of the dissepiments,
proceeds as far as the mesophyllic parenchyma, growing
into the intercellular spaces, and forms either a globose,
elongated, or irregular-shaped cell.
S iz e . Adult cell 0-T mm. diam.
W rig h t in Trans. Koy. Irish Acad. xxvi. (1877), p. 13.
Archer in Quart. Journ. Mior. Sci. xv. (1875), p. 104.
Living in the thallus of Lenina trisulca. Westmeath (Ire land).
Cohn says of this species: “ Its zoospores attach themselves to the
thallus of the duckweed often iu hundreds. They force their way
through between the epidermal cells, assuming, as the foremost portion
gets into the hypodermal tissues, a more or less figure of eight-shaped
form; the foremost portion, getting into an intercellular space, dilates ;
the portion that has not entered remains unexpanded, and forms a
colourless nipple-like projection ; the portion within the thallus expands
to many times its original diameter, sometimes dilating and filling up an
intercellular space, at others distorting the subadjacent cellular tissue,
and frequently itself becoming variously distorted. The cell wall becomes
thicker, even laminated ; the chlorophyll contents get dark and dense,
and the cell becomes of a dark, nearly opaque green; sometimes starch
granules are seen. The cell contents become segmented, breaking up into
a number of pear-shaped zoospores, which escape through the nipple-like
projection ; their actual exit was not seen, nor was the number or position
of the cilia observed. Of the zoospores, many never succeeded in penetrating
the epidermis of the duckweed upon which they alighted, and
such would remain as minute colourless pin’s heads on the surface of the
Lemna. Some would linger within the niothei' cell, and might possibly
be resting spores.”—A bstrac tly Prof. Perceval Wright, loc. cit.
Plate L X X X I. fig. 9. Chlorochytrium Lemnec parasitic on duckweed.
Zoospores located in intercellular spaces X 600. Kg. 10, in a more
advanced stage x 600. Fig. 11, free zoospores x 600. After Cohn.
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C l a s s I I . P IIY C O C H EOM O PH Y C EÆ .
Plants one or many celled, living in water, or enclosed in a
maternal jelly when out of it, mostly in families formed from
successive generations of cells. Cell membrane (Cytioderm)
not siliceous, combustible. Cell contents (Cytioplasm) a brown,
olivaceous, or fuscous endochrome, destitute of nucleus, and
usually without starch granules.
Propagation by division, and by immovable gonidia, or
quiescent spores.
O r d e r I. C Y S T IP H O EÆ .
Unicellular plants. Cells sphærical, oblong, or cylindrical
enclosed in a tegument, associated in families surrounded by a
universal tegument, immersed in a more or less liquid or firm
mucilage, variable in colour, for the most part irregularly disposed.
Division of the cells taking place in one, two, u r
three directions alternately. Propagation by quiescent gonidia.
Foeoundation unknown.
F a m i l y I. OHROOCOCOAOBÆ.
Thallus mucous or gelatinous, amorphous, enclosing cells and
families irregularly disposed.
It may be urged that, as many of the species included m this family,
as well as in the analogous Palmellaceoe, are only conditions of higher
forms, they should not have been inserted. In the preparation of a 1 lora
of this kind, however, we are of opinion that whilst the life history of
these forms is so imperfectly known, we should not have been justified m
excluding them.
Genus 81. CHROOCOCCUS. Nageli. (1849.)
Cells globose, or more or less angular from mutual pressure,
solitary, or associated in globose cubical or amorphous families,
free (not involved in a mother-cell). Cell membrane in most
cases thin, homogenous, achromatic, often confluent m a more
or less firm jelly ; cell contents verdigris, or pallid blue green,
not rarely yellow or orange. Propagation by division alter-
nately in three directions.
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