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58
THE MARINE ALGÆ OF NEW ENGLAND.
SUBORDER BOTRYDIEÆ.
Fronds minute green unicellar [sic], spherical or pyriform, with a rhizoidal process
at the base. Globose bodies produced in the cells, from which, when discharged,
there is formed a large number of zoospores, with two cilia, which conjugate.
A small suborder, of which the development is known only in a single species, B. granulatum, of which
Rostafinski and Woronin have given a full account. Probably the suborder may require to be united
with the Siphoneæ, a group abundant in the tropics, but not strictly found with us.
CODIOLUM, A. Br.
(Named from the resemblance to species of Codium, a genus of marine algæ.)
Frond unicellular, at the base prolonged into a tapering, solid, hyaline stalk, above
clavate, containing an oval chloropyllaceous mass, which ultimately is transformed
into a large number of spores, development of spores unknown.
The present genus was founded by A. Braun on a species found by him at Helgoland in 1852 and
described and figured in his work on unicellular algæ. A second species (C. Nordenskioldianum) was
described by Kjellman.
The genus is placed by Braun and Kjellman near Characium, but until the development of the spores
has been made out the position of the genus must remain doubtful. Braun compares the spores to those
of Codium, but states that he had never seen cilia. In American specimens we have never seen the
spores escape from the mother cell and swim about by means of cilia, but, on the other hand, the wall of
the mother cell dissolves and the spores thus set free begin to grow at once. It often happens that the
spores begin to grow inside the mother cell. The spores are oval and have a thick wall. Each spore
either gives off a projection at one end, which grows into a long stalk, or else the contents of the spore
become divided into a small number of cells by means of cross-partitions at right angles to its longer
axis, thus forming a short filament, each cell of which gives off a stalk as previously described. There
results in the last case a dense cluster of individuals, which adhere together by their bases. It may be
that what we have seen was only the hypnosporic condition of the plant, and that Braun had examined
a stage in which motile spores existed. Occasionally one finds two spore-bearing cells on a single stalk,
one always being very much smaller than the other. The second cell is lateral and may be nearly sessile
on the stalk or furnished with a short secondary stalk of its own.
Our plant recalls the hypnosporic condition of Botrydium granulatum, and in the Algæ Am. Bor. Exs. it
was distributed under the name of B. gregarium. As the development is so little known, we have now
thought best to retain the name Codiolum, on the supposition that our species is the same as that of
Braun. The study of the development is rendered difficult because the plant grows inextricably
entangled with other small algæ.
C. GREGARIUM, A. Br. (C. gregarium, Braun, Alg. Unicell., Genera nova et minus
cognita, p. 20, Pl. 1.—Botrydium gregarium, Farlow, in Alg. Am. Bor. Exs., No. 99.)
Cells densely aggregated, average length of cells, including stalk,