The Botany of Iceland - 01.12.1928, Qupperneq 91

THE AERIAL ALGÆ OF ICELAND
415
As will appear from the list above of the samples in which it was
found, this form is distributed throughout the island and occurs on the
ground, in almost all kinds of localities, most frequently, however, among
Prasiola and mosses. It has also been found on walls at oniy a small
height above the ground.
Hantzschia amphioxys var. genuina Grun. Grunow' Die Diat. Fr.
Jos. Ld. 1884, p. 47.
E. Icel. 41, 61, L. 68, 131 — N. Icel. 218 - N. W. Icel. L. 269 —
W. Icel. L. 307 — S. Icel. 295 — Vestmannaeyjar L. 401, L. 408, 409.
This variety is rarer in Iceland than var. xerophila, in company
with which it often occurs. From the material at hand it has not been
possible to infer what life conditions the two forms respectively require.
Nitzschia Grun.
Nitzschia amphibia Grun. V. Heurck Syn. Pl. 68, flg. 15,16. Cl.etGrun.
Arct. Diat. p. 98.
E, Icel. 7, 8, 14, 24, L. 25, 28, 41, 77, 78, 85, L. 92, L. 99, 112 —
N. Icel. L. 135, 140, 173, 215 — W. Icel. 321, 337 - S. Icel. 294.
The species is common in fresh water (0strup 55 samples from
Iceland), nor is it evidently uncommon on land, where I have often
found it on rocks with trickling \vater and on rather damp ground near
the edges of ditches. I have reason to believe that it will not withstand
much desiccation, whereas it seems very tolerant of organic matter in
the substratum (sample No. 173, »soil saturated with urine«) and capable
of thriving on purely mineral ground.
— — var. acutiuscula Grun. V. Heurck Syn. Pl. 68, flg. 19—22. Cl.
et Grun. Arct. Diat. p. 98.
N. Icel. 162.
Only one specimen observed.
Nitzschia Clausii Hantzsch. Grunow 1878 p. 119. Van Heurck Syn.
Pl. 66, íig. 10.
E. Icel. L. 7, L. 133 — N. W. Icel. L. 264 — S. Icel. 386 — Vestmanna-
eyjar 410.
I have sometimes found somewhat denser carinal dots than recorded
by Grunow, viz, 14 in 10/r. N.angnilliila Schum. can hardly be distinguished
from N. Clausii.
Ostrup having found lhe species in 14 samples from fresh water,
it can hardly be said to be a pronounced aérial species. I found it in
the largest quantity in the samplcs from roads and their vicinity (133,
264) where there will always be some manure. The same will be the
case with sample 410 from a bird-clifT. It would, however, be premature
to draw wider conclusions from this fact.