The Botany of Iceland - 01.12.1928, Qupperneq 85

THE AERIAL ALGÆ OF ICELAND
409
sumed that he referred specimens of P. parva v. minuta within the limits
in whicli I understand this form to this species.
I have most frequently found this form on damp rocks covered
with moss and on purely mineral ground (samples 25, 61, 68, 69, 129,
137, 253), but also in the vicinity of houses where it must be presumed
that some manure was present.
Pinnularia stauroptera Grun. v. interrupta Cl. Cl. Syn. II, p. 83. V. H.
Syn. Pl. 6 fig. 6.
N. Icel. 140.
Found in a ditch among desiccated algæ.
Pinnularia subcapitata Greg. Cl. Syn. II, p. 75. Van Heurck Sjm.
Pl. VI, fig. 22. Fig. nostra 30 h.
E. Icel. 4, L. 114, 123, L. 125 — N. Icel. 169, 173. L. 217, L. 218,
L. 256 - N. W. Icel. 269 - W. Icel. L. 307, L. 338.
In several of the samples tliere occurred specimens which were
considerably smaller than the typical form (L. 22 (u, br. 4,4 ju), thus in
samples 217 and 218, but apart from their size these small
specimens agree perfectly with the typical P. subcapitata.
For Denmark I came to the result (1915, p. 293 and
297) that P. subcapitata probably thrives equally well in
fresh water and on land. The same seems to be the case
in Iceland where 0strup found it in 51 samples from
fresh water. while I found it in 12 localities on land.
These, however, were of rather diverse kind, partly moss
on the ground and rocks, partlj' naked earth, partly from
the neighbourhood of hot springs, partly places near human
habitations abounding in organic substances. Hence it is
diflicult to form any idea as to what life conditions it
would require in order to thrive well. Deflandre found
the species on damp rock in Normandy (1926).
— — var. sublanceolata n. var.
L. 17—22 p, br. 4,6/«, str. 11—14 in 10 /i. Valve lan-
ceolate with slightly rostrate, occasionally quite slightly
capitate, ajiices, in all other particulars resembles tlie species. Fig. 30 a.
E. Iccl. 69, L. 125 - N. Icel. 160, L. 218.
In samples 125 and 218 this variety was found in company with
the species. Found only on moss on rocks and on fairly pure mineral
ground.
Pinnularia viridis Nitzsch var. commutata Grun. Cl. Syn. 11, p. 91.
Van Heurck Syn. Pl. 5, tig. 6.
E. Icel. 8, 25, 40, 92, L. 99, 124, L. 125, L. 128 — N. W. Icel. 140,
169, L. 217, L. 218 - W. Icel. 298.
Fig. 30.
Pinnularia
subcapitata
Greg. a. var.
sublanceo-
lata n. var.
b. f. typica.
(X 1200).