The Botany of Iceland - 01.12.1928, Side 80

404
JOHS. BOYE PETERSEN
I have previously (1924 III, p. 17) had occasion to point out that
Cleve’s diagnosis of this species is erroneous (Syn. II, p. 80), whereas
Lagerstedt’s original description íits the case very well. Possibly it
was Cleve’s description that led Hustedt astray, so that he used the ,
name in »Die Bacillariaceen Vegetation des Sarekgebirges* 1924 about
a form that is quite distinct from the present form and evidently belongs
to the forms centring round P. parva.
Like most of the Pinnularia species, P. intermedia shows considerable
variation in the shape and size of the valve, as also in the closeness
and direction of the striation. There are, however, several characteri-
stics which recur more or less distinctly in all the forms:
1. The striæ come extremely close to the raphe.
2. The striæ nearest to the transapical fascia are not shortened (see,
however, Lagerstedt 1873, Taf. I, flg. 3a).
3. The striæ are radiate in the middle and converge at the apices.
In very short forms they are occasionally almost parallel.
4. In the larger forms the striæ are broader near the raphe than at
the margin of the valve. In smaller forms this is less pronounced
but is often seen quite distinctly.
5. In all the forms mentioned below there will occur specimens that
are slightly constricted in the middle.
In the Icelandic material I have been able to distinguish between
the following forms, between which intermediate forms often occur,
especially within the two groups into which I have divided them. t
A. Smaller forms.
f. 1. Valve oblong-elliptical with rounded apices. L. 22—26 p,, br. 4,6—
5,2 /r, str. 12 in 10/t. Fig. 24 a.
f. 2. Valve elliptical with rounded or slightly cuneate apices. The
striæ are frequently almost parallel. L. 13—15 /t, br. 4,5— 5,5/r, str. abt. 9.
Fig. 24 b, c.
f. 3. Valve linear, with broad, truncate, somewhat produced capitate
apices, more or less constricted in the middle. L. 24 /t, br. 5,9 /u, str. 9—
10. (Boye P. 1915, p. 293, fig. 19 belongs to this form). Fig. 24d.
B. Larger forms.
f. 4. Valve linear, constricted in the middle with a slight gibbosity
here, so that the valve becomes slightly triundulate; apices cuneate-
truncate or rounded. L. 33 /t, br. 7,0/t, str. 8,2 in 10/t. Fig. 24 e.
f. 5. Valve linear, with rounded apices. L. 24 /u, br. 6,6 /u, str. abt. 8
in 10/t (Lagerstedt 1873, Taf, I, flg. 3ax). Fig. 24f.
C. Somewhat doubtful form.
f. 6. Valve linear, somewhat constricted in the middle, with pointed
cuneate apices. L. 22 p, br. 5,5 /u, str. abt. 12 in 10/t. Seems to show
most afflnity to f. 1. Fig. 24 g.
These forms were distributed as follows: .
f. 1. E. Icel. 7, L. 40, 69, 77, 113, L. 129 — N. Icel. 160, 162, L. 179, 182,
L. 184, 217, 219, L. 241, L. 253 — N. W. Icel. L. 268 — W. Icel.
L. 307 — S. Icel. L. 295, L. 353.
J