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REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 11
have shown to be erroneous views with regard to the structure and development of
the different species, and Harvey’s three classes no longer serve as a basis for
classification. The Melanospermeæ and Chlorospermeæ are entirely rearranged, and
although the Rhodospermeæ are still considered to form a natural group, the older
name, Florideæ, employed by Agardh, is used to designate them. The basis of
classification is the structure of the fruit and the organs of fructification, in the
knowledge of which a great advance has been made during the last twenty years.
CRYPTOPHYCEÆ.—The lowest of all the algæ are those which belong to the order
Cryptophyceæ, in which, as yet, the only reproduction known is by means of nonsexual
spores and hormogonia. Most of the species of the order are bluish green, but
some are purplish, brown, or even pink. The bluish-green coloring matter is due to
the presence of phycochrome, which is a mixture of chlorophyl and phycocyanin. The
last is extracted by water when the algæ containing it are bruised, the chlorophyl
being soluble in alcohol. The species of Cryptophyceæ consist of cells which are
usually roundish, or disk-shaped, and which are generally held together by a mass of
gelatinous substance which surrounds them. The order is divided into two
suborders, according to the arrangement of the cells in relation to the jelly. The first
suborder, the Chroococcaceæ includes all the species in which the cells are either
isolated or arranged in amorphous or more or less spherical masses. Some of the
species of this suborder are very small, and in some of the modern classifications are
placed with the Bacteria, in the order Protophytes. The mode of growth of the
Chroococcaceæ is by division of the cells, first into two, then into four, and so on. The
masses which they form may be called colonies, each cell forming a distinct
individual, which is usually capable of living apart from its fellows. Spores, which
are known in only one species, are formed by some of the cells enlarging and taking
on a thick cell-wall. Nothing like sexual reproduction is seen either in this or the
next suborder.
NOSTOCHINEÆ.—In the second suborder of the Cryptophyceæ, the Nostochineæ, the
cells are always attached to one another in the form of filaments, to which the name
of trichomata is given. The trichomata may either be free, as in Oscillaria (Pl. I, fig.
5), inclosed in a sheath, as in Lyngbya (Pl. I, fig. 4), or packed in a dense mass of
jelly, as in Rivularia (Pl. II, fig. 2). The cells composing the trichomata are usually
disk-shaped or cylindrical, but are sometimes nearly spherical.
Besides the ordinary cells, we find in many species a second kind of cell,
distinguished from the others by its glassy appearance and its yellowish or brownish
rather than bluish-green color. (Pl. I, fig. 3, a; fig. 6, b; Pl. II, figs. 1 and 2, a.) They
are called heterocysts, and are found sometimes scattered amongst the other cells,
and sometimes at the end of the trichomata, their position often serving as a generic
character. The reproduction of the Nostochineæ takes place in two ways, by
hormogonia