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THE MARINE ALGÆ OF NEW ENGLAND.
SUBORDER SPONGIOCARPEÆ.
Fronds solid, cylindrical, branching; antheridia in spots on upper part of fronds;
tetraspores cruciate, immersed in the cortical filaments; cystocarps in external wartlike
protuberances, composed of parallel filaments, spores obovate, densely packed
around the surface of a cellular mass which surrounds the tip of a short pedicel.
The present suborder was made by J. G. Agardh and Harvey to include a single species, Polyides
rotundus, a species in several respects anomalous. The development of the cystocarps of that species
was first made out by Thuret and Bornet, and a detailed account Was published in the Études
Phycologiques. In its development the cystocarp of Polyides resembles that of the genus Dudresnaya.
There is produced from the cells at the base of the trichogyne a number of filaments which wind
amongst the short filaments, of which the wart-like bodies near the tips of the fronds are formed; These
filaments come in contact with certain cells of the protuberances, which then divide and produce the
spores. Although this indirect fertilization of the carpogenic cells by means of winding filaments is the
same as is found in Dudresnaya, the mature cystocarp is different in the two genera. In Polyides the
ripe spores are arranged in a regular layer around a small placenta, which is borne on a short pedicel
produced from the carpogenic cell. In Dudresnaya coccinea the spores are irregularly grouped, around a
placenta surrounding the carpogenic cell itself. In L. purpurifera, however, according to D. Bornet, the
cystocarps more nearly resemble those of Polyides, and he thinks it not impossible to unite the two
genera in one suborder.
POLYIDES, Ag.
(From πολυς [polus], many, and ιδεα [idea], form.)
Fronds cylindrical, dichotomous, composed of interlaced branching filaments,
consisting of elongated cells and curving outwards at the surface so as to form a
cortical layer of horizontal filaments; antheridia in patches on the upper part of
frond, consisting of short, densely packed filaments bearing clusters of antherozoids;
tetraspores cruciate, immersed in the cortical layer; cystocarps in wart-like
protuberances on the upper part of the frond.
P. ROTUNDUS, Grev.; Phyc. Brit, Pl. 95.
Fronds blackish red, cylindrical, cartilaginous, three to six inches long, attached by a
disk, with an undivided stipe, which becomes above repeatedly dichotomous, apices
obtuse; warts flesh-colored, numerous on the upper divisions of the frond.
On stones in deep pools and in deep water.
Common from New York northward; Europe.
A species easily recognized by its regularly dichotomous, cylindrical frond, by its dark, almost black,
color, and dense cartilaginous substance. When sterile it might be mistaken for Furcellaria fastigiata, a
common species of Northern Europe, which may be expected to occur on our coast. In fruit, however,
they are easily distinguished, since the cystocarps of Polyides are borne in external warts, while those
of Furcellaria