The Botany of Iceland - 01.12.1914, Síða 138

322
THORODDSEN
plants are common: Potentilla anserina, Leontodon autumnalis, Tri-
folium repens, Brunella vulgaris, Gnaphalium uliginosum and G. sil-
vaticum, Hydrocotyle oulgaris, Ranunculus acer, Sagina procumbens,
Sperguta arvensis, Plantago major, P. maritima f. pygmœa, Polygonum
persicaria, P. aviculare and various Gramineæ, and sometimes Vicia
cracca. Where it is damper occur Epilobium palustre, E. alsini-
folium, Cardamine multicaulis, Montia rivularis, Limosella aquatica,
Juncus tamprocarpus, J. bufonius and some Carices. The composition
of these groups of species differs however considerably at the dif-
ferent kinds of springs. Of vascular plants the following have been
observed exclusively near alkaline hot springs: Hydrocotyle vulgare,
Gnaphalium uliginosum, Veronica anagallis, Polygonum persicaria;
rare outside the range of influence of hot springs are Galeopsis te-
trahit, Plantago lanceolata, P. major and Blechnum spicant. Moreover,
C. Ostenfeld enumerates eight species of mosses which have been
found only on warm soil, and three species which are especially
connected with a warm ground. In North Iceland some species
grow only near hot springs, which in South Iceland thrive also
outside the area of the warm soil, for instance, Brunella vulgaris,
Plantago lanceolata, Cardamine multicaulis and Drosera rotundi-
folia. In the outlets from both the warm and hot springs an abun-
dance of algæ often occurs — often in a great heat — which have
not as yet been investigated. Near solfataras vegetation is ex-
tremely sparse, and in the immediate neighbourhood of the sul-
phurous-acid fumaroles no plant-life can thrive, therefore only bare
clayey flats occur there. Ophioglossum vulgatum grows only near
solfataras; in 1882 I found at Bjarnarflag near Myvatn scattered,
but numerous, specimens of it on elayey ground which had a tem-
perature of 27 °C. — it occurred together with Sagina procumbens and
Poa pratensis; and in 1883 I found it near Gunnuhver on Reykjanes
also on warm clay in the neighbourhood ol' sulphur springs. In
both localities it occurred together with the otherwise rare Riccia
bifurca and Chomocarpon commutatus. C. Ostenfeld found it on
Reykjanes in the neighhourhood of steaming holes, “first a crust
was found held together by a Stigonemaspecies, then a great many
Muscineae of which the most characteristic were Riccia bifurca and
Chomocarpon commutatus. Amongst them occurred some other mosses:
Pohlia nutans v. fdicaulis, Fossombronia Dumortieri, Bryum ventrico-
snm, Fissidens osmundioides and Philonotis fontana, moreover, the cha-
racteristic Ophioglossum vulgatum var. polyphylta" (loc. cit. p. 240).