THE DUAL-LICHEN HYPOTHESIS. 
107 
three species of Discomycetes in the Falkland Islands, to 116 
Lichens. The Reindeer Moss and species of Umbilicaria flourish 
amongst the snow. On the other hand, frost and snow are fatal 
to Discomycetous Fungi, which disappear long before the snow- 
line is reached on mountains, and even before phanerogamic vegeta- 
tion in the direction of the Polar regions. Of all plants. 
Lichens support extreme cold most successfully, whilst Fungi 
succumb at the approach of frost. 
Lichens which grow upon the bark of trees may be seen flourish- 
ing in profusion during the life and vigour of the tree. It has been 
affirmed that the portions of Cinchona Bark which have been covered 
with Lichens during growth, abound in the Alkaloids on which 
their medicinal use depends,* whereas the portions attacked by 
Fungi are valueless from the tissue being destroyed by the ramify- 
ing mycelium. Indeed, Fungi do not, and cannot flourish on 
growing and vigorous bark, but on diseased, dead or decaying spots. 
Lichens obtain the greater portion of their pabulum from the 
atmosphere, and only their mineral constituents from the matrix. 
Hence they cover the trunks and branches of forest trees, without 
apparent injury, and many species habitually flourish on the hardest 
granite. Fungi, on the other hand, obtain their chief support from 
the decaying vegetable matter on which they flourish, gathering up 
a large store of the nitrogenous results of putrefaction and decay, 
and disintegrating the matrix on which they prey. 
Lichens, in their chemical composition, contain a large number 
of substances which are wholly unknown amongst fungi. Colorific 
principles, such as obtain in the Orchella weeds, Orcellic, Cetraric, 
Lecanoric, Tannic and Gallic Acids, Lichenin, and even a pecu- 
liar and characteristic odour, all of which cannot be attributed to 
the gonidia they contain. 
Lichens contain but a small percentage of water as compared 
with Fungi, so that in dessication they do not shrivel, collapse or 
perceptibly diminish in size, whereas Fungi shrivel up and collapse 
so as scarcely to be recognised, becoming liable constantly to the 
attack of insects, or, if damp, subject to the development of mould, 
whilst Lichens may be preserved for years under like conditions 
without fear of insect or mould. 
Lichens, when collected and cast aside without the slightest care 
or precaution, do not exhibit the least tendency to putrefy, whilst 
Fungi, with the utmost care in drying, can scarce be preserved 
from unmistakable evidences of incipient putrefaction. 
* Pharmacologists are aware that the most valuable kinds of Cinchona 
Bark, as, for instance the “ Crown Bark,” are habitually covered with 
Lichens, and that this covering favours the development of the Alkaloids. 
Regarding this fact, the late Mr Mclvor, of Ootacamund, introduced the 
plan of covering the growing branches of Chinchona plants with moss, and 
the bark thus mossed produced a larger percentage of Alkaloids than the 
naked bark. The operation may be purely mechanical, such as obstruct- 
ing the light. However this may be, certainly no injury is inflicted, but 
benefit is conferred by the growing lichens. 
