The Botany of Iceland - 01.12.1928, Side 70

394
JOHS. BOYE PETERSEN
rostratis; striis punctatis radiantibus vel apice parallelis; area apicali
angusta; area centrali rotundata vel in fasciam transapicalem unilatera-
liter vel bilateraliter dilatata. Fig. 19.
Long. 9—24 //, lat. 5—6,3 /t, striis 18—20 in 10 //.
E. Icel. L. 131 — N. Icel. L. 161, L. 162, L. 173, L. 242, L. 252, 256 —
N. W. Icel. 268 - W. Icel. L. 297, L. 298, L. 309, 327 — S. Icel. L. 282,
L. 295, L. 352, L. 353, L. 372, L. 381.
A rather variable species of which,
however, I do not find any reason to set
up varieties since the various forms are
found intermixcd among each other and
with transitional forms. Quite small
specimens occur of oval shape with
rounded or slightly truncate apices
Fig. 19. Naoicula nitrophila (19/<, br. 5/<, str. abt. 20), and with a
Boye P. n. sp. (X 1200) round central area. Larger specimens
occur with nearly lanceolate valves wilh
rostrate apices, with the central area round or more or less transversally
expanded. sometimes reaching the edge of the valve on one side. (L. 12—
17 //, br. 6,2/1, str. 18). Finally large specimens are found in which the
valve is linear with rostrate apices and a broad transapical fascia. (L. 24/*,
br. 6/<, str. 18). These specimens somewhat resemble N. Borrichii but
differ plainly from this species in the striæ not being radiate at the
apices and especially by their appearance in the girdle view. The valves
are slightly silicified which often gives them an irregular appearance as
a consequence of the preparation. I have found the species in 18 samples
in all, ncarlv all derived from the immediate vicinity of houses, in ])laccs
where there was abundant manure and therefore a copious vegetation
of Prasiola crispa and other nitrophilous species. (In 14 of the 18 samples
it was found among Prasiola crispa). Navicula nitrophila itself must there-
fore be regarded as a pronounced nitrophilous spccies. Everything
would seem to indicate that it will withstand strong desiccation, it having
in many cases been found on fences.
Navicula Rotæana Rabh. var. oblongella Grun. Cleve Syn. I, p. 128.
Van Heurck Syn. Fl. 14, fig. 21.
E. Icel. 25, 129 - W. Icel. 297, 298 - S. Icel. 295.
The median striæ were somewhat wider apart than the rest, the
spaces between these wcre very sttiall so that they were almost confluent,
a striation which is also found e. g.
few specimens were found in each
could cell contents be obscrved.
m N.pupula Kútz. Only
sample, and in no case
rrn
U
Navicula thermicola Boye P. n. sp.
Valvis oblongis, producto-capitatis, long. 13//, lat. 3,3//,
striis in medio 18 in 10//, aj)ices versus densioribus; area
apicali angusta, area centrali in fasciam transapicalem dila- Boyép.'msp.
tata; nodulis terminalibus in costas apicales protractis. Fig. 20. (X 1200).
Flg 21).
Navicula
thermicola