Chaetomorpha aerea (Dillwyn) Kütz.

NEW YORf-
SOTANICAI.
G Aï? Dì
? N
2. Chaetomorpha aerea (Dillw.) Kuetz.
Plate 14, figs. 9-11
Filaments rigid, erect, dark green becoming yellowish with age,
nearly cylindrical throughout except at the tapering base, attached
by delicate rhizoids issuing from the lower end of the basal segment
and later coalescent into a more or less solid disk, 125—300/a diam.;
segments at first cylindrical, later varying to almost spherical in the
fertile segments, 0.5-2 times as long, basal segments much longer;
membrane hyaline, thick, at times lamellate; chromatophore at first
continuous, finely fenestrate.
Growing in rock pools along high-tide limit or even above. Com-
mon on the coast of California from Monterey to San Diego.
1920]
S et chell-Gar einer : Chlorophyceae
201
Kuetzing, Sp. Alg., 1849, p. 379; Collins, Green Alg. X. A., 1909,
p. 324; Collins, Ilolden and Setchell, Phyc. Bor.-Amer. (Exsicc.),
no. 76. Conferva aerea Dillwvn, Brit. Conf., 1809, pi. 80.
We feel reasonably safe in referring certain specimens from the
central and southern coasts of California to this widespread species
after carefully comparing them with specimens from the European
and New England coasts. Our plants favor shallow rock pools, more
or less lined with sand and situated high up in the littoral belt where
the water is warmed by the sun. The specimens available for exam-
ination are rather young and range from 200/x to 300^ above. The
filaments are erect and tufted, and collapse on being taken from the
water. The plants are grass green below but lighter and yellowish
above, the color dying away at the tips. This species does not seem
to form entangled masses above and we have found no specimens
corresponding to the Chaetomorpha Lininn of the New England coasts
and those of Europe, which is supposed to be a state or variety of
C. aerea. We do not find plants over 300,u in diameter in any of our
specimens, whether in those from our own coasts or those from New
England or Europe. This is less than the extreme measurements given
by some writers (e.g., 600-700/* for zoosporangia by De-Toni. 1889,
p. 273) but agrees well with those given by Farlow (1881, p. 46) for
the New England plant. The basal segment is short, never ranging,
in specimens examined, over 1.5 mm. in length. The upper segments
in specimens approaching maturity are short, usually from 0.5 to
once as long as broad, but the lower segments may be as much as twice
longer than broad. The segments in fertile condition, or approaching
it, are slightly swollen and short barrel-shaped.
Tig.
X 35.
Figs.
stages.
Chaetomorpha aerea (Dillw.) Kuetz.
9. A group of young plants showing long basal cells with rhizoids.
10, U. Sketches showing different ages of the cells in vegetative
X 35.
NEW YORK BOTANICAL GARDEN