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enabled to place it in tbe group of Algæ to which it truly belongs.
By Professor A g a r d h it is regarded as a species of Scytonema,
but that excellent observer probably never saw it growing; and
every one who bas studied tbe Algæ at all, is aware of the difficulty
of determining the structure of minute kinds from dried
specimens; besides, from the figures published iu D i l l w y n ’s
“ Confervæ,” and in “ English Botany,” it is quite impossible
to ascertain the real nature of the plant ; nor do either of them,
indeed, represent the enlarged filaments correctly. L y n g b y e
has admitted it into his Tentamen Hydrophytologiæ Danicæ,
but has given no figure ; nevertheless it is clear he has not the
right plant, for in the specimens before us, there is nothing resembling
“ annuli distantes, aurantii, moniliformes and besides,
he says his specimens do not change in drying, which the
true plant invariably does.
In habit and mode of branching, this species approaches
the genus ScMzonema, but it is really tubular, and the granules
form no parallel lines : when the filament divides, it is
independently of the arrangement of the granules, the reverse
of which s the case in the true ScMzonemata.
When I described M. Dillwynii, I had some suspicion
that Conferva comoides might not prove to he diflFerent. Having
subsequently seen the latter in a living state, I have no
doubt they are distinct. The very habit of growth in M. comoides
is peculiar : it does not grow in solitary tufts, but often
takes entire possession of the surface of rocks for many yards
together, especially such as have been worn smooth by the action
of the waves ; and on flat coasts, where a very thin layer of
mud is deposited on them, it thrives remarkably freely. It occurs
where it is exposed to be covered at every tide, but is not
met with in deep water.
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Fig. 1. M. comoides, natural size ( represented as itjtoats in the water) . Fig. 2.
Portions o f Jilaments. Fig. 3. A portion o f a filament, plicate on the concave
side, in consequence o f being artificially curved under the microscope,
thus shewing the existence o f a membrane. Fig. 4. Granules : magnified.
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