PDF file (text) - Cryptogamic Botany Company

104
THE MARINE ALGÆ OF NEW ENGLAND.
and which is found floating and infertile in the course of the Gulf Stream and in the so-called Sargasso
Sea, between 20° and 45° N. and 40° W. It is rarely washed ashore in New England, but is frequently
brought in by fishing vessels. It is said that there is a large mass of this sea-weed in the ocean not far
from Nantucket, but there is no definite information on the subject. The species in its floating form is
distinguished from the last by its narrower leaves, destitute of cryptostomata, its darker color, and
denser habit.
SUBORDER VAUCHERIEÆ.
Comprising a single genus, Vaucheria, whose characters are given below.
VAUCHERIA, D. C.
(Named in honor of Jean Pierre Vaucher, of Geneva.)
Fronds green, unicellular, composed of long, irregularly or falsely dichotomously
branching filaments, monœcious or diœcious; oogonia sessile or stalked, containing a
single oospore; antheridia either short ovoid sacks or formed at the tips of branches,
which are frequently spirally twisted; antherozoids very small, with two cilia; nonsexual
reproduction by very large zoospores, which are covered with cilia, or by
motionless spores formed at the ends of short branches.
The Vaucheriæ abound both on our coast and in inland waters, and some species grow upon damp
ground in gardens and meadows. They either form thick turfs of a dark-green color when growing in
places which are not constantly submerged, or else extend in indefinite-shaped masses when growing
where there is plenty of water. They are generally easily recognized at sight, and are known under the
microscope by the long branching filaments of a deep-green color, destitute of cross-partitions except
when the fruit is forming. Although very abundant on our shore, the species are little known, because
the specific characters depend upon the fruit. The determination of sterile specimens is out of the
question, and, even when fruiting, dried specimens are of comparatively little value. A considerable
number of species of Vaucheria have been described, but as a great part of them have been described
from individuals bearing the non-sexual spores only, recent writers, as Walz and Nordstedt, have
reduced the number of species very much by omitting imperfectly characterized forms. Nordstedt
admits nineteen species in Europe. The American species have never been critically studied. Specimens
should be kept in fluid rather than mounted on paper, and sketches of the fruit should be made at the
time of gathering. It should not be forgotten by the collector that some of the species are diœcious, and
also that a species is not perfectly known unless the non-sexual spores are described as well as the
oospores.
V. THURETII, Woronin, Beit. zur Kenntniss der Vaucherien, in Bot. Zeit., Vol. XXVII,
p. 157, Pl. 2, Figs, 30-32.
Monœcious; filaments .03-8 mm in diameter, forming short, dense turfs; antheridia
sessile, oval, .05-7 mm broad by .10-14 mm long; contents of antheridia colorless; oogonia
either sessile or on short lateral branches, obovoid or pyriform, inclined, .25-30 mm
long by 20 mm wide; oospores spherical, .15-18 mm in diameter, yellowish brown; cellwall
rather thin;