Acrochaetium alcyonidii C. C. Jao

Acrochaetium Alcyonidiae, sp. nov.
(PI. 12, figs. 2-4)	v ¡S
Filamentis basalibus endozoicis, valde longioribus quam filamentis erectis,
intra hospitem penetratis, raro partibus epizoicis, abunde at plerumque rli-
chotomiter ramosis, cellulis plerumque medio tumidis, 6.5-13/i latis, 13-32/i
longis; filamentis erectis usque ad 600/i altis; ramulis plerumque 1- 5-, inter-
dum ad 10-, cellularibus, brevissimis, secundis vel sparsis, cellulis 6.5-9.5,u
latis, 9.5-19/i longis; sine pilis; chromatophoro parietali, pyrenoideo centrali
instructo; monosporangiis obovoideis, sessilibus vel pediculo unicellulo, 1 vel 2
in ramulorum articulissingulis, terminalibus vel secundis,plerumque densecon-
fertis, 8.0-9.5m latis, (13-) 16-19/i longis, interdum bisporangiis repositis.
Plants endozoic below, the basal filaments much longer than the erect fila-
ments, deeply penetrating into the host between the individuals of the colony,
rarely a part of them epizoic, abundantly and usually dichotomously branched,
the cells varying in size and shape, 6.5-13/i diameter, 13-32/i long, often swol-
len in the middle; the free filaments erect, up to 600/i long, with very short
branches, which are usually 1-5, sometimes up to 10 cells long, secund or scat-
tered, cells 6.5-9.5/i diameter, 9.5-19/i long; hairs absent, occasionally the
terminal cells gradually much tapered toward the end, but containing chro-
matophores; chromatophore single, parietal, with a prominent central py-
renoid; monosporangia obovoid, sessile or with a 1-cell stalk, 1 or 2 on each
articulation, terminal or secund, very rarely otherwise, in crowded groups on
short branches, 8.0-9.5p. diameter, (13-) 16-19/i long; occasionally replaced
by bisporangia.
This species differs from Acrochaetium Daviesii (Dillwyn) Naegeli in
having a strongly marked endozoic habit and very short lateral branches.
In size and habit it is near to Acrochaetium endozoicum (Darbishire) Hamel,
but A. endozoicum has shorter free filaments with copiously forked
branches as shown in Darbishire’s drawings, and much shorter monospor-
angia.
Found on Alcyonidium Mytili Dalyell, washed ashore in Sheep Pen
Harbor, Sept. 1, 1934. Type in C.-C. Jao collections and Herb. Univ.
Mich., Woods TIole No. 279.
BULLETIN OF TIIE TORREY CLUB	[VOL 63
I'igs. 2-4. Acrochaetium Alcyonidiae Jao, sp. nov. Figure 2, cross section of Al-
cyonidium Mytili Dalyell, showing the endozoic habit of the Acrochaetium plants, X42,
figure 3, detail of adult plants, X360, figure 4, adult plant, showing the bispcrangia
and part of the epizoic basal filament, X360.
/
JAO: RHODOPHYCEAE
NEW YORK BOTANICAL GARDEN
02141473