The Botany of Iceland - 01.12.1928, Side 77

THE AERIAL ALGÆ OF ICELAND
401
Pinnularia appendiculata Ag. var. irrorata Grun. Van Heurck Svn.
P1.VI, íig. 31.
E. Icel. 8. L. 41, L. 61, 78, 124? — N. Icel. 135, 169, 217, 218, L. 253,
L. 254, L. 256 — N. W. Icel. L. 269 — W. Icel. 307, L. 321, 336.
On measuring Van Heurck’s figure (1. c.) I found the following
dimensions: L. 18,9 /i, br. 3,4 /t, str. 25 in 10 p. This shows a fairly close
agreement with a number of specimens which I found in the Icelandic
samples. One of these is shown in fig. 22. Its dimensions
were: L. 15,6 /u, br. 3,9 /u, str. 23 in 10 [x. The valve was in
the main linear, with a thickening in the middle and at the
ends. The mediau striæ were somewhal more strongty marked
than the rest. The striæ radiated in the middle, converging
slightiy at the apices. Apical area narrow, only slightly ex-
panded around the central nodule. The only particular in
which I íind some deviation from Van Heurck’s flgure is
that the median striæ are somewhat more shortened in that
figure than in the specimens observed by me. Cleve in-
cludes the present variety within Pinnularia appendiculala. It
seems to me that he goes too far. In the material I have
examined I have not found any intermediate forms. In sample
169, however, I found a form approaching P. Oculus 0str. by its strongly
capitate apices, but differing from that form by its smaller size and
finer striation (L. 15 p, br. 4 p, str. abt. 24). In other samples I found
shorter specimens whose apices were very indistinctly capitate.
I found the present form in rather diverse locatities, both among
mosses and algæ on purely mineral ground, in places near houses
abounding in manure, and near hot springs.
Fig. 22.
Pinnularia
appendicu-
lata Ag. var.
irrorata
Grun.
(X 1200).
Pinnularia borealis Ehrb. Cl. Syn. II, p. 80. V. H. Syn. Pl.VI, fig. 3, 4.
A. Schm. Atl. Pl. 45, fig. 15-21.
E. Icel. 4, 7, 8, 14,15, 28, L. 40, L. 41, L. 61, L. 68, L. 69, 70, L. 77,
78, L. 85, L. 92, 112, L. 113, 114, L. 121, L. 123, L. 125, L. 128, 129, 131 —
N. Icel. 135, 137, 138, 140, L. 160, 161, L. 162, 169, 173. L. 182, 184,
L. 185, L. 196, L. 217, L. 218, L. 219, L. 241, 242, 252, L. 254 — N. W. Icel.
L. 268, 269 — W. Icel. 298, 307, L. 309, L. 321, L. 327, 336, 338 — S. Icel.
282, L. 295, L. 352, L. 353, L. 372, 373, 381, 387.
P. borealis is a highly variable though generally easily recognisable
species. Cleve mentions (1. c..) that it shows a transition to P. lata, and
conversely I should think that transitional forms to P. Balfouriana might
be found. In the course of time a number of different forms, often
termed varieties, have been described and figured. Ehrenberg already
mentions some (see de Toni Syll. Alg. Vol. II, Sect. I, p. 20). Some have
been mentioned later and described by more recent authors, others have
not been mentioned. Subsequentlj' a number of fortns were figured in
A. Schm. Atl. (1 c.) without any special designation. Moreover a couple
of forms have been described byPantoczek and Greguss (Greguss
1913, p. 214, Taf. VII, fig. 68, and Taf. VI, fig. 39) and by Carlson (1913,
p. 21, Taf. III, fig. 15) I shall not ntake more detailed mention of all