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116
THE MARINE ALGÆ OF NEW ENGLAND.
tetraspores lining the walls of immersed conceptacles, zonate, cruciate, or
irregularly placed; cystocarps unknown.
A small genus, comprising half a dozen species, which form thin crusts on rocks and stones both in salt
and fresh water. The systematic position of the genus is doubtful, and must remain so until the
cystocarps are known. Since the tetraspores are borne in special conceptacles, the genus has been
placed by some writers with the Corallineæ, although the species are not strictly calcareous. By others
it is placed with the Squamarieæ. Antheridia are only known in H. rivularis, where they are said by
Borzi to be long cylindrical cells formed from the superficial cells of the thallus, each cell containing a
number of spherical antherozoids arranged one above another.
H. ROSEA, Kütz. (H. rubra, Harv., Phyc. Brit., Pl. 250; Farlow, in Report of U. S. Fish
Comm. for 1871.)
Fronds thin, closely adherent to the substratum, cells of nearly the same size in all
parts of the frond; conceptacles numerous, completely immersed, spherical;
tetraspores either zonate or irregularly divided, lining the walls of the conceptacles
and mixed with filiform, slender paraphyses.
On stones and rocks near low-water mark.
Everywhere common.
One of our commonest species, which forms continuous thin crusts, often of considerable extent, tinging
the rocks with a pinkish or somewhat brownish color; not easily mistaken for any other alga on our
coast, except possibly young forms of Petrocelis, which is, however, thicker, more velvety in appearance,
and darker in color.
Suborder NEMALIEÆ.
(Heminthocladieæ, Agardh & Harvey.)
Fronds more or less gelatinous or occasionally coated with a calcareous deposit,
filamentous, branching, formed of an axial portion composed of elongated
longitudinal filaments, which give off short, corymbose, horizontal branches, which
constitute the cortical portion; antheridia in tufts on the superficial cells; cystocarps
immersed in the frond, borne on the peripheral filaments, composed of densely
packed chains of spores radiating from a central cell, either without any proper
envelope, or with a filamentous involucre or surrounded by a proper membranous
pericarp; tetraspores?
A comparatively small suborder, comprising species whose fronds, except in color, resemble the fronds
of the Chordarieæ in the Phæosporeæ, since they consist of an axis composed of longitudinal filaments
and a cortex of short, much-branched horizontal filaments. All our species are soft and somewhat
gelatinous, but the species of Liagora, which abound in the tropics and are found in Southern Europe
and in this country in Florida and California, have a more or less distinct coating of carbonate of lime.
The procarps and cystocarps in this suborder are very simple. There are a few species belonging to the
genus Batrachospermum which occur in fresh water. In that genus the formation of the cystocarps is
very simple. The trichogyne and trichopore are represented by a single large cell, constircted [sic] near
the base. After fertilization the chains of spores are formed directly from the part below the
constriction. In