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REPORT OF THE COMMISSIONER OF FISH AND FISHERIES. 15
and spring than at other seasons, if we except a few genera, like Ectocarpus. The
conjugation in this suborder was first seen by Areschoug in Dictyosiphon, and
afterwards by Goebel in Ectocarpus pusillus. The zoospores unite in nearly the same
way as in the Chlorosporeæ. According to Goebel, who studied the zoospores coming
from plurilocular sporangia, the conjugation occurs between zoospores coming from
different sporangia. The development of the zygospore and the action of the
zoospores borne in the unilocular sporangia, except in the genus Dictyosiphon, are
not yet satisfactorily known. Thuret and Bornet have seen bodies which they
consider to be antheridia in several species of Ectocarpus, and Pringsheim at one
time considered that he had found antheridia in a species of Sphacelaria. It is now
admitted that the bodies found by Pringsheim belonged to a parasitic species of
Chytridium, and Thuret and Bornet were unable to ascertain the development of the
antheridia in Ectocarpus. At any rate, nothing like an oogonium or any female organ
to be fertilized by the antherozoids has been found in the Phæosporeæ.
As has already been hinted, the genera of Phæosporeæ differ from one another very
widely in the structure of the frond. From low forms, consisting of short filaments,
we pass upwards, through various cylindrical, crustaceous, and globose forms, to the
highly developed devil’s aprons, Laminareæ, the largest of our sea-weeds; and,
finally, on the coast of California and in the Antarctic Ocean, we find the perfection
of the order in the enormous Macrocystis pyrifera, which is several hundred feet
long; the Nereocystis or bladder-kelp of California; and Egregia, in which we have
what appears to be a separate stem, leaves, bladders, and fruit-bearing leaves.
Janczewski distinguishes three principal modes of growth of the thallus in
Phæosporeæ. The first consist in growth from a single terminal cell, as in
Sphacelaria, Cladostephus, and Dictyosiphon, resulting in the formation of a
filamentous solid plant. The second mode consists in the simultaneous growth of
several contiguous filaments at their tips, so as to form either a flat expansion, as in
Myrionema and Ralfsia, or a more or less globular body, as in Leathesia. The third
mode is illustrated by the genus Laminaria, in which there is a stalk, a blade, and
root-like growths. The place of growth is at the point of union of stem and blade, and
the new blade, which begins to form at the tip of the stem, grows upwards from the
base and gradually pushes off the old blade. In Scytosiphon a similar mode of growth
is found only here, there being no stalk, the growth is at the base of the plant.
During a certain part of the year, especially in the spring, most of the Phæosporeæ
are covered with delicate hairs, which disappear as the plant becomes old.
The suborder contains a large number of species, which are divided into several
families. Those found on our coast are the following:
SCYTOSIPHONEÆ.—This family includes the two genera Scytosiphon and Phyllitis,
which comprise the old Chorda lomentaria and Laminaria