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106
THE MARINE ALGÆ OF NEW ENGLAND.
and at the time, as there were no antheridia, we hastily inferred that the spores were non-sexual. It
now seems probable that the plant is the V. litorea of Nordstedt, l. c., a diœcious species. The species
was common at Wood’s Holl in August, 1879, but constantly sterile. The antheridia of V. litorea,
Nordstedt, are long and cylindrical and borne on a short sterile cell at the tips of the branches. The
antherozoids are discharged by openings at the apex and sides of the antheridium. Our plant will be
easily recognized by its habit and the recurved branches bearing the oogonia.
ORDER IV. FLORIDEÆ.
Algæ of a red or purple color; antheridia containing spherical, hyaline antherozoids,
which are without cilia; sexual fruit or cystocarps developed from a procarp, which
consists of a trichogyne, at whose base is a trichophore, the spores formed either
from the trichophore or the adjacent cells which compose the carpogenic system;
spores at maturity either naked or inclosed in a pericarp; non-sexual reproduction by
tetraspores, bispores, and seirospores; fronds filamentous, crustaceous,
membranaceous, or irregularly expanded, varying from gelatinous to cartilaginous
in substance, occasionally calcareous. Principally marine.
The Florideæ, which are the same as the Rhodospermeæ of Harvey, include a large number of species,
all of which have some shade of red, although it may be nearly black on the one hand or approach
shades of green on the other. In decay, however, the color becomes orange and finally green. It is not to
be inferred, however, that all red algæ belong to the Florideæ . There are a few Cyanophyceæ in which
the color is pink, but in these species the frond is merely an agglomeration of red cells, each of which is
practically a distinct individual, whereas in the Florideæ the cells are organically united, and constitute
a single plant. The structure of the frond in this order varies in the different genera, and we have forms
which correspond closely to the fronds of the Phæosporeæ, as, for instance, in Nemalion we have a frond
which, apart from its color, is undistinguishable from that of Mesogloia, and so on. The non-sexual
reproduction is by tetraspores, cells which divide into four parts—rarely by bispores or two-parted
cells—and seirospores, or chains of oblong cells formed directly from the branches. The sexual fruit,
known as the cystocarp, is developed from a procarp, as has already been explained. The division into
suborders is founded principally on the differences in the cystocarpic fruit, the full development of
which is not known in many cases. Differences in the fronds and tetraspores serve to mark the genera.
Agardh and Harvey divide the Florideæ into two series—the Desmiospermeæ, in which the spores are
arranged in a definite series with regard to a placenta or common point of attachment, and
Gongylospermeæ, where the spores are heaped together without order. A study of the development,
however, shows that this distinction has not the value which it was formerly supposed to have, and
certain suborders with differently arranged spores are by those who lay stress upon the development
placed in proximity to others in which the spores are irregularly grouped. Although, owing to modern
researches, we know much more about the real nature of the cystocarps than was known a few years
ago, it must be admitted that the suborders of Florideæ are far from satisfactory. As a matter of fact,
the order is a very natural one, and, as is the case with most natural orders, the species and genera
pass so gradually into one another that sharply marked divisions are out of the question. At the base of
the order is a small number of genera whose position is doubtful, owing to our lack of information about
the fructification. Then come the Porphyreæ, in which we have fronds of a single layer of cells
(Porphyra) and certain cells grow out so as to form a very short