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170
THE MARINE ALGÆ OF NEW ENGLAND.
cell. The peripheral cells are similar to one another and of the same length as the central cell, and, as
the successive secondary cells lie exactly or nearly exactly over one another, the mature frond appears
to be composed of a central filament or axis surrounded by a number of secondary filaments or siphons,
as they are termed in speaking of the present genus and its allies. There is formed in some species a
second set of cells alternating with the siphons, and also corticating, generally irregularly sinuous cells,
which cover the surface. The tetraspores, according to Prof. E. P. Wright, are formed by out-growths
from the axial cell. The antheridia are borne on the delicate, colorless filaments which form tufts on the
younger parts of the frond. The filaments are dichotomous and the antheridia cover the lower cells of
one of the forkings, the branch sometimes being prolonged beyond, when the antheridia are said to be
mucronate. The cystocarps are terminal on short branches, and contain within a pericarp, whose cells
are arranged in longitudinal series, pyriform spores on short stalks around a small basal placenta.
Some of our species are not well defined, and a prolonged observation on the shore, especially during
the spring months, is necessary before the limits of some species can be accurately fixed.
SECT. I. Siphons four, cortications wanting.
P. URCEOLATA, (Dillw.) Grev.; Phyc. Brit., Pl. 167.
Fronds deep red, becoming blackish, cæspitose, three to ten inches high, setaceous,
branches subdichotomous, with short, alternate, patent or recurved, decompound
branchlets, siphons four, cells below 4-5 times longer than broad, becoming shorter
above; cystocarps on short lateral branches, urceolate, with a distinct neck;
antheridia linear-oblong, mucronate.
Var. FORMOSA, Ag. (Polysiphonia formosa, Phyc. Brit.)
Filaments soft and flaccid, branches long, flexuous, branchlets somewhat
attenuated, cells 5-10 times as long as broad.
Var. PATENS, Grev. (P. subcontorta, Peek, Twenty-third Report New York State
Botanist.)
Branches numerous, recurved or revolute.
On wharves and rocks at low-water mark.
From New Jersey northward; Europe; California.
A common perennial species, most abundant in the spring, when it has a deep blood-red color. It is
frequent on old wharves and wood-work and on the under surface of rocks near low-water mark, where
it forms small turfs, in company with Callithamnion Rothii. The var. formosa is found only in the
spring, and is softer, forms longer tufts, and has longer cells than the type. It is the only form of the
species which adheres well to paper or which can lay claim to beauty. It is especially luxuriant in April
at Wood’s Holl and the region of New Bedford, and forms dense tufts sometimes a foot long. As usually
seen in summer, the species is blackish and setaceous and covered with diatomes. The var. patens,
which differs somewhat in general habit from the type, is not uncommon with us. Through the kindness
of Mr. Peck, we have been able to examine a specimen of his P. subcontorta, which, judging from the
description in the Twenty-third Report, seemed to be closely related to, if not a form of, P. Harveyi. An
examination of the specimen, however, seems to us to show that it is var. patens of the present species,
which it resembles in microscopic characters.
P. subtilissima, Mont.
Filaments densely tufted, two to four inches long, purplish brown,