The Botany of Iceland - 01.12.1928, Page 90

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JOHS. BOYE PETERSEN
Rhopalodia ventricosa (Kútz.) O. M. Meister 1912, p. 201, Taf. 35, fig. 8.
E. Icel. 7, L. 25, 28, 78, 85, L. 92 — N. Icel. L. 135, 140, 184.
This very widespread species occurred in a fairly great number of
specimens in a quantity of samples, and was found with cell contents
in samples from rather dry localities (92, 135). It is thus certain that
it may occur as an aérial species, though it is evidently much commoner
in fresh water. (Ostrup 196 samples).
X. Nitzschieæ.
Hantzschia Grun.
Hantzschia amphioxys (Ehrb.) Grun.
It has long been known that certain forms of this species are of
common occurrence on the ground, thus by Pfitzer (1882 p. 405). Var.
xerophila, in particular, is recorded by Grunow from such localities,
but in reality forms that must be referred to var. genuina Grun. are no
less common on the ground as I have previously stated (Boye P. 1915
p. 294). It has been observed by Deflandre on damp rocks (1926).
In cultures of soil from various depths Moore and Karrer (1919, p. 296)
found the species very common down to a depth of 100 cm. According to
renewed investigations by Mooreand NellieCarter (1926) Hantzschia
did not prove very common in the samples of soil examined. It was
found, however, in two samples from a depth of down to 2 feet 6 inches.
B. Muriel Bristol instituted a series of cultures of soil-samples (1920,
p. 42) which had been dried for a shorter or longer period. In nearly
all of them she found small forms of H. amphioxys which must pre-
sumably be referred to the two ahove-mentioned varieties of Grunow.
The samples had been dried for 4—26 weeks, so these experiments show
that the species has a very considerable power of withstanding desicca-
tion. I found (1915 p. 275) that H. amphioxys was alive and able to
move in a preparation in water of a sample of soil only containing
5,2 p. c. of water.
— — var. xerophila Grun. Grun. Diat. Fr. Jos. Ld. 1884, p. 47.
E. Icel. L. 14, L. 15, L. 40, L. 68, L.77, L. 78, L. 92, L. 121 — N. Icel.
135, L. 137, 138, 160, L.162, L.173, L.182, L.185, L.196, L. 217, L. 218,
L. 219, L. 241, 252 a, L. 253, L. 254 — \V. Icel. L. 298, L. 307, L. 309 a,
L. 321, L. 327 — S. Icel. L. 282, 295, L. 352, 353, 372, L. 381, 387, 395 —
Vestmannaeyjar L. 407, L. 408, L. 409.
According to Grunow (1. c.) var. xerophila has the same appearance
as var. gentiina which is stated to be furnished »mit stumpfen, etwas
vorgezogenen Enden». In most of the Icelandic specimens of var. xero-
phila the apices were plainly capitate and often somewhat upward curved,
there were, however, some specimens whose apices were simply produced,
In a single sample (68) there were some specimens with two pronounced
gibbosities on the ventral side near the apices, and in other samples,
too, something similar was found, but in less marked degree.