The Botany of Iceland - 01.12.1928, Side 63

THE AERIAL ALGÆ OF ICELAND
387
Stauroneis parvula Grun. var. producta Grun. Cl. Syn. I, p. 149.
V. Heurck Syn. Pl. IV, fig. 12.
E. Icel. 85.
Only few speciniens observed.
Navicnla Bory.
Naviculœ minusculœ Cl.
Navicula Atomus (Nag.) Grun. V. Heurck, Traité des Diat. p. 227,
Pl. 5, fig. 230.
E. Icel. L. 8, 14, L. 92, L. 114, L. 121, 128, L. 131 — N. Icel. L. 133,
L.162, L.173, L.179, L. 182, 218, 219, 241, L.252, L.254, L.256 —
N. W. Icel. L. 269 - W. Icel. L. 297, L. 307, L. 309 a, 321, L. 327, L. 336 —
S. Icel. L. 282, L. 295, L. 352, L. 372, L. 373, L. 381, L. 387, 395 - Vest-
mannaevjar L. 409.
Area: Eur., Jan Mayen.
A pronounced terrcstial species, as has been recognised already by
a number of investigators. e. g. Cleve, V.Heurck, and v. Schönfeldt.
I have previously found that this species could keep alive in soil con-
taining only 6,8 p. c. of water (1915 p. 7), and by culture Miss Bristol
found the species (1920) in several samples of soil that had been dried
for up to 8 weeks. The species has thus a very considerable power of
withstanding desiccation.
Already my experience from Denmark (1915, p. 290) seemed to in-
dicate that this species especially thrives well in rich soil containing
much organic matter, perhaps particularly such as abounds in nitro-
genous nourishment and with neutral or alkalic reaction. Miss Bristol’s
samples of soil mostly originate froin similar localities. Of the 33 samples
from Iceland in which I found the species, 20 were taken in the imme-
diate vicinity of human habitations where there is always plenty of
manure, and probably such substances have been present in several of
the other localities, too. In 15 of the samples examined it was found
in company with Prasiola crispa. Kolkwitz and Marsson (1908 p. 513)
class the species as /S-mesosaprohe.
I have previously (1915, p. 21) descrihed the extremely hyaline
frustules of this species. They are most strongly silicified around the
raphe and viewed from the girdle side they are quite narrow. Hence
Miss Bristol’s fig. 9,10 (1920) can scarcely belong to this species but
seems to represent a species with much more solid frustules, perhaps
one of the small forms of Navicula mutica (?). I have also pointed out
that larger forms than those described hy Van Heurck may often be
met with. In the Icelandic material I have found similar large forms,
e. g. in sample 219, in which one specimen had the dimensions: 1. 13,6 fx,
br. 6,6 p, str. in the middle abt. 14, towards the apices abt. 23 in 10 /u.
This specimen likewise showed a distinct transapical area.
The species has undoubtedly very often passed unnoticed, hence it
is difficult at the present moment to form any opinion as to its distri-
bution, but in all probability it is very widespread.