106 
THE DUAL-LICHEN HYPOTHESIS. 
then lichens, irrespective of the gonidia, should correspond in all 
respects to the Fungi to which they are referred. The presence of 
these small organisms may be ignored in our comparison of the 
supposed fungus with the real fungus of our experience. 
In comparing the general character of Lichens with the general 
character of Fungi, we may assume that we can arrive at some 
definite conclusion as to the probability of their identity. We can 
predicate nothing of fungi except what is confirmed by fact ; and 
any other organisms to be affiliated to them must agree in all main 
features with the known characters of the Fungi, or they can have 
no claim to be considered identical. 
It will facilitate this comparison if we are enabled to limit the 
area, which may be done by accepting the limitation fixed by the 
Schwendenerian hypothesis that the Ascomycetous Fungi are meant 
when the term Fungi is used, and as the Sphceriacei have been vir- 
tually excluded by all advocates of the theory, it may be assumed, 
as has been admitted, that the Discomycetes are the special group of 
Fungi to which the Lichens are referred. 
The Discomycetes , in their cup-like forms are assumed to be 
identical with the apothecia of certain lichens, nay, more than this, 
all Lichens, to whatever genus they may belong, in their totality, 
excepting only their gonidia, are affirmed to be Discomycetous 
Fungi. 
“ Lichens are perennial ; they grow very slowly, but they attain 
an extreme age. Some species growing on the primitive rocks of 
the highest mountain ranges in the world, are estimated to have 
attained an age of at least a thousand years ; and one author 
mentions, after the lapse of nearly half a century, having observed 
the same specimen of Sticto pulmonaria on the same spot of the 
same tree.”* 
On the other hand the Discomycetous Fungi are annual, very 
short-lived, their whole existence being limited to a few weeks, 
rapid in growth, and rapid in decay, not a trace of some species 
remaining after a few days. 
Lichens will exist under conditions of aridity which no other 
vegetables could support. Some are peculiar to calcareous rocks, 
a few are found on arenaceous rocks, many are common on the 
granitoid series, including micaceous, gneissic, granitic and quartz- 
ose rocks, and Lecidea geographica is frequent on the purest and 
smoothest quartz. 
Fungi, on the contrary, must have moisture for their very exist- 
ence sake, are mostly found in damp and shaded situations, and 
could never exist under the conditions just enumerated for 
Lichens. 
The highest mountains, beyond the snow-line, at 16,000 feet 
on Chimborazo, the extreme limits of vegetation at the North and 
South Pole are occupied by Lichens. Dr. Hooker found 
* Dr. Lauder Lindsay, “ Lichens,” p. 52. 
