Acrochaetium subseriatum Børgesen

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Acrochaetium subseriatum, sp. nov.	'... „ o;•;? •
(PI. 11, figs. 5-7)	3-fZ
Thallo epiphytico, cellula basali elongata, membrana crassa, filis repenti-
bus depravatis e cellula basali et cellula adjacentia ramosis; filum erectuiti a
spora mutabili orientem, altitudine usque ad 2—3 mm., a basi magna parte
ramosis, ramis inferioribus valde longioribus quam superioribus; ramis se-
cundariis crebris, secundis vel alternis; cellulis 6.4-9.6/* altis, 32-70/1 longis;
244	BULLETIN OF THE TORREY CLUB	[VOL. 63
pilis terminalibus, rarissimis; chromatophoro parietali pyrenoideo centrali
instructo; monosporangiis sessilibus vel pediculo unicellulo, secundis prope
basim ramorum, raro sparsis, cvlindrico-ovatis, 6.5-9.5ju altis, 22-31/i longis.
Plants epiphytic; basal cell elongate, with a thick wall, with the adjoining
cell giving rise to contorted creeping filaments; solitary erect main filament
arising from the modified spore cell, up to 2-3 mm. tall, freely branched, the
lowest branches quite near the base, much longer than the upper ones, gradu-
ally shorter upward, branchlets very numerous, secund or alternate, cells
6.4-9.6/i diameter, 32-70/i long; hairs terminal, very rare; chromatophore
parietal, containing a central pyrenoid; monosporangia mostly borne on each
articulation of the branchlets, sessile or with 1-celled stalks, secund near the
base of the branchlets, rarely scattered, cylindric-obovoid in form, 6.5-9.5/x
diameter, 22-31/i long.
These plants are related to Acrochaetium seriatim B^rgcsen and A.
Sagraeanum (Mont.) Bornet, but differentiated from both in that erect
filaments do not arise from the creeping filaments, and the cylindric-
obovoid monosporangia are much longer. The basal part of A. seriatiim
B0rgesen consists of short, irregularly bent, creeping filaments, fusing
together in the middle into a small disc. In A . Sagraeanum (Mont.) Bornet
the basal layer is composed of contorted and entangled filaments, from
which the erect filaments arise.
Plants epiphytic on Zostera, mixed with Acrochaetium virgatulum var.
luxurious. Collected from Nobska Point, Woods Hole, Massachusetts,
Aug. 25, 1933. Type in C.-C. Tao collections and Herb. Univ. Mich., Woods
Hole No. 278.
BULLETIN OF THE TORREY CLUB
VOLUME 63 PLATE 1 1
NEW YORK BOTANICAL GARDEN
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tec Figs. 5-7. Acrochaetium subseriatum Jao, sp. nov. Figure 5, habit drawing of an
adult plant, X84; figure 6, detail of branchlets bearing monosporangia, showing ripe
and regenerating sporangia and chromatophores, X360; figure 7, detail of holdfast, A ;
X360.
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rv- NiCAL
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