sheath
diffuse, without a definite outline |
Click on the thumbnail for a larger image |
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Mucilage
sheath may only be visible with the aid of Indian Ink: cells crescent-shaped
or twisted |
Kirchneriella: forms coenobia of 2,4,8..32 cells
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Sheath
may be indistinct, but cells are clearly linked in pairs by dichotomous
branching threads radiating from the centre; chloroplast a parietal cup
+ 1 pyrenoid.. |
Dictyosphaerium
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Sheath of very dense mucilage, almost obscuring cells |
Botryococcus: cells rounded or elongate; colony
contains yellow oil droplets which can be squeezed out under a coverslip,
sometimes forms green to yellow-orange blooms.
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Sheath
with a firm outline |
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layered
(lamellate); |
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cells spherical/elliptical, chloroplast parietal cup + pyrenoid
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Gloeocystis:sheath may be concentrically
lamellate
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with
concentric lamellations; cells spherical, chloroplast stellate
(see second image)
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Asterococcus: concentric lamellations not always
present, chloroplast form may be difficult to see also
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Sheath
plain, not layered: |
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sheath sac-like, cells with pseudocilia extending through the sheath
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[Pseudocilium
= flexible, but not motile, projecting fibre]
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(a) colony normally
attached at 1 end
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Apiocystis
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(b) colony planktonic
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Tetraspora?
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no
pseudocilia, spherical cells
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in groups of 4,
8, 16 within a spherical sheath
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?
Sphaerocystis:
(coenobium)
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in groups
of 4 or 8 in tight tetrads or in a wreath-shape |
Coenochloris
or Coenococcus: no illustration available; considerable
scope for confusion between these (and Sphaerocystis), and some
doubt whether they are different.
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in groups
of 2-4 cells in mucilage sheath, with semicircular mother-cell wall remnants
lying between; chloroplast a parietal cup, 1 pyrenoid |
Schizochlamydella:
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Similar genus: Westella
- cells in 4's, sometimes arranged quadrately, linked by mother-cell
wall remnants
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no
pseudocilia, oval cells
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Cells
apparently oval or kidney-shaped, in pairs, linked together: actually
desmid semicells |
Cosmocladium: a colonial desmid; the cells reminiscent
of Cosmarium
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Cells
ranging from spherical to oval or spindle-shaped (depending on species),
in coenobia of 2,4,8,...64, within a mucilage sheath composed of gelatinised
mother-cell wall |
Oocystis
: chloroplast(s) parietal plate or trough, with or without a
pyrenoid
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Cells
solitary or in coenobia enclosed by mother-cell wall; cells somewhat kidney-shaped,
with one side curved and the opposite nearly straight |
Oonephris:
chloroplast stellate, but often shape not readily distinguishable
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Coenobia
of 4 cells in a flat, quadrate arrangement; cells various shapes |
Crucigenia
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Coenobia
in a flat, quadrate arrangement; cells oval, or tapering to one end, often
with a space in the centre. Cells in groups of 4 enclosed by mucilage
sheath, sometimes connected to 3 other coenobia by mother cell-wall remains,
all lying in same plane |
Crucigeniella
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cells elongated,
cigar-shaped
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cells
pointed, banana-shaped in groups of 4 which all lie parallel and aligned. |
Quadrigula
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cells
as Quadrigula, with bundles of cells parallel but not aligned. |
Pseudoquadrigula
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cells elongated,
spindle-shaped or tapering
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Grouped
in 2's or 4's with alternate cells pointing in opposite directions, linked
by mother-cell wall remnants, in a diffuse mucilage sheath |
Dichotomococcus
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Similar
genera:
Quadricoccus (cells more oval)
Forming coenobia linked in a wreath-like formation:
Komarekia
Crucigenia (some species)
Coronastrum |
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Genera not included:
Botryosphaerella, Ecballocystis,Elaktothrix, Granulocystopsis, Hormotila,
Juranyella, Palmodictyon, Paulschulzia, Schizochlamys,
Sphaerobotrys
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