Acrochaetium attenuatum (Rosenv.) Hamel

Acrociiaetium attenuatum (Rosenvinge) Hamel 1927
(PI. 12, fig. 1)	5(p4
Plants epiphytic; basal filaments fused together near the center to form a
1-layered disc, ramification mostly dichotomous or opposite, irregularly ex-
tended from the center, cells 6.5-9.5/x diameter, 6.5-1 1m long; erect filaments
numerous, arising from the central part of the basal disc, up to 250 (or more)/*
tall, ramification scattered, opposite or dichotomous, the terminal cells taper-
ing toward the tip and forming a terminal hyaline hair, cells 5.0-6.5/* diameter,
(6.5-) 9.5—16ju long; chromatophore parietal, with a prominent pyrenoid;
monosporangia occur mostly on the upper part of the plant and usually are
solitary, mostly sessile, sometimes with a 1-celled stalk, oval in form, 4.0-6.5/t
diameter, 6.5-9.6/i long.
These plants as described above seem to be very close to Acrochaetium
attenuatum (Rosenvinge) Hamel, except that the erect filaments are shorter
and hairs do not disappear on the longest filaments. Probably the writer’s
samples are in a rather young condition, but the growth habit and measure-
19361	JAO: RHODOPHYCEAE	245
ments are quite in accord. This species is newly recorded for North Ameri-
ica.
Found on Polysiphonia fibrillosa together with several other species of
Acrochaetium, Norton Point, Marthas Vineyard, Massachusetts, Aug. 3,
1934.
BULLETIN OF THE TORREY CLUB	VOLUME 63, PLATE 12
Explanation of plate 12
'9-£.Xil Fig- 1- Acrochaetium attenuatum (Rosenvinge) Hamel, X360.
02141474
NEW YORK
BOTANICAL
GARDEN
02141474