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68
THE MARINE ALGÆ OF NEW ENGLAND.
Var. FILIFORMIS. (M. filiformis, Harv., Phyc. Brit., Pl. 156.—M. Harveyana, Næg.
partim.)
Fronds filiform in outline, axis furnished only at intervals with branches.
On various algæ, especially Scytosiphon lomentarius.
Gloucester, Mass., Mrs. Bray.
Var. filiformis, Penobscot Bay, Maine, Hooper; Newport, R.I.; Europe.
A species forming small tufts on different Phæosporeæ, probably abundant on our coast, but as yet only
recorded in a few localities. Nægeli has shown, l. c., that the two species of Harvey are merely forms of
a single species, the variety filiformis being less fully developed than M. clavæformis, which was first
described.
ECTOCARPUS, Lyngb.
(From εκτος [ektos], external, and καρπος [karpos], fruit.)
Fronds filamentous, monosiphonous or occasionally partly polysiphonous by radial
division of some of the cells; plurilocular sporangia ovate, cylindrical or siliculose,
consisting of numerous small cells arranged in regular longitudinal and transverse
series; unilocular sporangia cylindrical or oval, either stalked or formed by the direct
transformation of the cells of the branches.
The genus is here accepted in an extended sense, and includes a number of genera of modern writers
which we have preferred to consider subgenera. Perhaps Pylaiella should be kept distinct, as in this
subgenus both the unilocular and multilocular sporangia are formed by the direct transformation of
some of the cells in the continuity of the filaments rather than in special branches. But in Capsicarpella
we have the multilocular sporangia formed in the continuity of the branches as in Pylaiella, while the
unilocular sporangia are .partly emergent and seem to be intermediate between those of Pylaiella and
Ectocarpus proper. Streblonema, if separated from Ectocarpus by its creeping habit, resembles it
perfectly in its fruit, and, as the different species of Streblonema vary considerably as to their
procumbent habit, it seems, on the whole, better not to retain the genus. The described species of
Ectocarpus proper are very numerous, but unfortunately they are not well characterized. The greater
part of the species may be grouped around E. confervoides and E. fasciculatus as types, but exactly how
far differences in ramification and dimensions of the sporangia are to be considered specific rather than
mere variations is a matter about which botanists do not agree. One thing is certain, that specific
analysis has been carried too far in this group, and it is especially true with regard to the species of
Kützing. In describing a species of Ectocarpus it is important to have both the unilocular and
plurilocular conditions. In most of the species, however, only one form is known. The unilocular
sporangia are often difficult to determine, because the Ectocarpi, especially those growing on dirty
wharves, are infested by parasites, Chytridium, &c., which produce globular swellings of the cells,
which might then, especially in dried specimens, be mistaken for unilocular sporangia.
Besides the two forms of sporangia, Thuret and Bornet have recorded the existence of bodies to which
they have given the name of antheridia. It has been suggested that the antheridia were cells distorted
by parasites. We have never seen antheridia in American specimens, and are not in a position to
express any opinion. The fact that a conjugation of the zoospores has been observed by Goebel in E.
pusillus