Acrochaetium erectum Børgesen

TWres	Three plants with monosporangia
Fig. 1. Acrochaetium erect uni Boergs.
(x 250) _______
Acrochaetium erectum Boergs., sp. nov. ; A. Dufourii
proximum, quod tamen filamentis erectis pluribus, thallo magis
racemoso, cellulis brevioribus, sporangiis brevioribus et crassioribus
praecipue distinguitur.
Thallus usque ad 400-500 ¡j. altus e cellula basali oritur
iilum emittente erectum plus minus ramosum e cellulis cylindricis
5 [x latis et 12 ¡i. longis compositum. Rami sparsi aut secundati,
rarissime oppositi. Chromatophorum parietale, pyrenoide laterali
instructum. Sporangia sessilia aut pedicellata, ellipsoideo-sub-
cylindrica, 10 ^ longa, 5 [a lata.
India. Dwarka, upon Agardhiella robusta, Boergesen 5431
(type).
The basal cell (Fig. 1) is partially immersed in the thick cuticle
of the host and is usually a little longer than broad, namely 8-9 \l
long and 5-6 [x broad. I have always found only a single erect stem
from the spore. In most cases this erect stem is not ramified below
and many of the specimens consist only of the short main filament
from which a few sporangia or quite short branches are given off.
The ramification is alternate or secund : I have only once seen two
pedicels with sporangia given off oppositely from the same cell.
The sporangia are sessile or pedicellate, oblong-cylindrical, 4-5 ¡jl
broad,10-11 ^long.
Of the many small species of Acrochaetium with a single basal cell,
our plant is especially reminiscent of A. Dufourii Collins growing on
Sargassum (Rhodora, vol. xiii, 1911, 187 ; compare Hamel, in
Revue Algolog., 1926, 111, fig. 18), but this is a more branched plant
with several erect filaments of shorter cells, and with shorter and
thicker sporangia.
Acrochaetium erectum Merga. sp. nov.
Eull. Misc. InFTTKewj 1932 (3):114.f. l.-TOk
NEW YORK BOTANICAL GARDEN
A. Dufourii Collins proximum, quod tamen filamentis
erectis pluribus, thallo magis racemoso, cellulis brevior-
ibus , sporangiis brevioribus et crassioribus praecipue dis-
tinguitur.
Thallus usque ad 400—$00 p. altus e cellula basali
oritur filum emittente erectum plus minus ramosum e cellu-
lis cylindricis 5 U latis et 12 u longis compositum. Rami
sparsi aut secundati, rarissime oppositi. Chromatophorum
parietale, pyrenoide,laterali instructum. Sporangia ses-
silia aut pedicellata, ellipsoideo-sub-cylindrica, 10 u
longa, 5 u lata.
India. Dwarka, upon Agardhiella robusta. Bgfergesen
54-31 (type).
The basal cell (Fig. 1) is partially immersed in
the thick cuticle of the host and is usually a little
longer than broad, namely 8—-9 u long and Jr—6 u broad.
I have always found only a single erect stem from the
spore. In most cases this erect stem is not ramified be-
low and many of the specimens consist only of the short
main filament from which a few sporangia or quite short
branches are given off. The ramification is alternate or
secund: I have only once seen two pedicels with sporangia
given off oppositely from the same cell. The sporangia are
sessile or pedicellate, oblong-cylindrical, 4-— 5 U broad,
10 11 u long.
Of the many small species of Acrochaetium with a
single basal cell, our plant is especially reminiscent of
A* Dufourii Collins growing on Sargassum (Bhodora, vol.
xliTT 1911,18?; compare Hamel, In .Revue Algolog.,1926, III,
fig. 18), but this is a more branched plant with several
erect filaments of shorter cells, and with shorter and
thicker sporangia.
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