The Botany of Iceland - 01.12.1928, Side 59

THE AERIAL ALGÆ OF ICELAND
383
3. Apices pointed.
a. Valve linear, apical area often wide.............. f. acala n. f.
b. Sides of valve form regular curves................ var. lenticularis 0str.
Common to all these varieties are the transapical fascia, the fairly
constant number of striæ (23—27 in 10/<), and the often quitc parallel
course of the striæ.
Caloneis fasciata var. typica. Navicula fasciata Lagerstedt 1873, p. 34,
Tab. II, flg. 11. V. Heurck Syn. Pl. 12, fig. 34.
E. Icel. 78?, 85, L. 99, L. 128 - N. Icel. 140, 169, 215 — W. Icel.
337 — Vestmannaeyjar L. 399, L. 410.
This form varies somewhat in size. The specimens measured from
various samples showed the following dimensions: L. 20—39,6 /t, br. 4,2—
7,7 /t, str. 23—27 in 10 fi. The largest were found in sample 410, the
smallest in sample 215. Curiously enough the largest specimens showed
the íinest striation.
Most (5) of the samples in which it occurred were derived from
rocks, most frequently from places with trickling water. Several óf the
other sainples were likewise derived from localities with water in plenty.
From this we may perhaps be permitted to infer that this form does
not withstand desiccation very well.
The sample containing most of the specimens was No. 410 from a
bird cliff. These facts would seem to show that it thrives best on a
mineral substratum but tliat nitrogenous nourishment even in plenty is
not harmful to it.
— — var. fontinalis (Grun.) N. fontinalis Grun. in V. H. Syn. Pl. XII,
íig. 33 b.
E. Icel. L. 7, L. 128, L. 129 — N. Icel. 217.
This variety, too, was somewhat variable in size. I have found the
following dimensions: L. 17—33 ju, br. 4,4—5,7/r, str. 23—27 in 10 ju. In
3 of the 4 samples it was found among mosses. None of the localities
were particularly drv or could be supposed to provide abundant nitro-
genous nourishment.
— — var. inconstantissima (Grun.). N. bacillaris v. inconstantissima
Grun. inV. H. Syn. Pl. XII, fig. 28. N. lacunarum Grun. V. H. Syn. Pl. XII,
fig. 31. N. fontinalis Grun. ibid. Pl. XII, fig. 33a (non. b!).
S. Icel. 282.
Navicula bacillaris v. inconstantissima Grun. as well as N. Lacunarum
Grun. and N. fontinalis Grun. seem to me to resemble each other greatly
by the regular linear form with rounded apices. The only difference
between them seems to me to be one of size.
In the above-mentioned sample 282 derived from soil by a manure
lieap near Heykjavík in vvhich thc Diatoms were found among Prasiola
crispa, there occurred a form with the dimensions L. 29 p, br. 7,0 p, str. 23
in 10/t.