Acrochaetium compactum C. C. Jao

Acrochaetium compactum, sp. nov.
(PL 10, figs. 6—14)
Thallo epiphytico, minutissimo, 22-42/i longo et 38—61^ alto (pilis exceptis);
cellula basli singula globosa vel subglobosa, membrana crassa, plerumque
grandiore quam filamentarum cellulis, circiter 8— 1 Opt alia; filis erectis plerum-
que 3, interclum 2 vel 4, a cellula basali ramosis, valde expandis, plus minusve
irregulariter ramosis, ramulis brevibus plantarum nitidarum frequenter fas-
cicularibus, apicem versus sensim paulum attenuatis, cellulis doliiformibus,
5-8/i altis, 5-10/i longis; pilis terminalibus; chromatophoro slellaeformi, pyre-
noideo centrali instructo; monosporangiis sessilibus, terminalibus, secundis vel
sparsis, raro oppositis, 1 vel 2 in articulis singulis, ovatis vel subglobosis,
5.0-6.5/i altis, 6.5-7.0/i longis.
Plants epiphytic, very small, 22-42/i tall and 38-61/i broad (except hairs);
basal cell single, globose or subglobose, with a thick wall, especially on the lower
side, generally larger than the filament cells, 8-10/i diameter, from which are
produced mostly three, sometimes two or four erect main filaments more ex-
panded in a single plane, more or less irregularly branched, branchlets of the
well developed plants frequently tufted, gradually slightly tapering toward the
end, cells barrel-shaped, 5-8/t diameter, 5-10/i long; hairs terminal; chromato-
phore stellate, with a central pyrenoid; monosporangia sessile, terminal, se-
cund or scattered, rarely opposite, mostly 1, sometimes 2, on each articulation,
ovate or subglobose, 5.0-6.5p. diameter and 6.5-7.0p. long.
These plants are related to Acrochaetium moniliforme (Rosenvinge)
B^rgesen and A. crassipes B0rgesen, but differ from the first in having
lesser dimensions of all cells and the branchlets tufted in well developed
plants, and from the second in having the filaments often more than two,
the basal cell globose in form, and the branchlets tufted.
Very abundant on Cladophora sp. from Black Rock, Sconticut Neck
near Pairhaven, New Bedford, July 25, 1934. Type in C.-C. Jao collections
and Herb. Univ. Mich., Woods Hole No. 275.
J4
Figs. 6-14. Acrochaetium compactum Jao, sp. nov. X605. Figures 6-8, three well
developed plants in different views; figures 9-14, young plants, showing the develop-
mental stages.
NEW YORK BOTANICAL GARDEN
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nEW YORK
BOTANICAL
GARDEN
02141486