Acrochaetium microfilum C. C. Jao

BULLETIN OF THE TORREY CLUB
BULLETIN OF THE TORREY CLUB
VOLUME 63. PLATE 10
Explanation of plate 10
Figs. 1-5. Acrochaetium microjilum Jao, sp. nov. X605. Figure 1, two fully de-
veloped plants; figures 2-5, four young plants, showing the earliest developmental
stages.
Acrochaetium microfilum, sp. nov.
(PI. 10, figs. 1-5)
^ )
Fronde minutissima, epiphytica, 40-60^ alta, 20-35,u longa (pilis exceptis);
cellula basali solitaria globosa, maiore quam filamentae cellulis, circa 6.5/u
diametro; fila plerumque 3, interdum 4, plana una sola et recta 2- vel 6-cellu-
lares gignente; fills exterioribus plus extentis, directis vel paulo recurvatis, in
hospite ferme decumbentibus; ramulis lateralibus vel dichotomis, cellulis
doliiformibus, 3-5 (-6)ju latis, 3-5 (-6)^ longis; cellula terminali apicem versus
sensim in pilum hyalinum attenuati; chromatophoro parietali, cellulam com-
plenti vel paene complenti, pyrenoideo centrali instructo; monosporangiis
regulariter secundis in filis aequis et secundis vel sparsis in filis erectis, ple-
rumque sessilibus, rarius pediculo unicellulo, forma ovatis, 3-5ju altis, 6.5-8.0ju
longis.
Plants epiphytic, very small, 40-60^ wide, 20-35 p. tall; basal cell single
and globose, larger than the filament cells, about 6.5p in diameter, with rather
thick wall, from which are produced often three, sometimes four, free main
filaments in a single vertical plane, 2-6 cells long, the outside two filaments
more extended, straight or slightly arched downward, almost decumbent on
the host, the remaining filament or filaments erect, branches lateral or dichot-
omous, cells barrel-shaped, 3-5 (-6)ju diameter, 3-5(-6)// long; the terminal
cell tapering toward the end to form a hyaline hair; chromatophore parietal,
filling or nearly filling the cell, witha central pyrenoid;monosporangia regularly
secund on the horizontal filaments, secund or scattered on the erect filaments,
mostly sessile, rarely with one-celled stalks, oval in form, 3-5m diameter, 6.5-
8.0yu long.
This species should be compared with Acrochaetium crassipes B^rgesen,
A. trifilum Batters, A. parvulum (Kylin) Hoyt and A. pule helium B^rgesen,
but it differs from the first in having the chromatophores not stellate, and
a globose basal cell; from the second in not having the monosporangia
globose; from the third in never having the monosporangia opposite in
arrangement; from the fourth in having the basal cell undivided, the fila-
ment not creeping on the host, but in a regular fan-shaped arrangement;
and from all of them in having smaller dimensions of all cells.
Found on Polysiphonia fibrillosa together with several other species of
Acrochaetium, Norton Point, Marthas Vineyard, Massachusetts, Aug. 3,
1934. Type in C.-C. Jao collections and Herb. Univ. Mich., Woods Hole No.
274.
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