AN INTRODUCTION TO THE STUDY OF LICHENS. 87 
posed fungus; and the coloured gonidia which are found in 
Lichens, the supposed alge. The fungus is said to be parasitic 
upon the green cells of the algz, holding them as prisoners and 
slaves, and by their activity nourishing its own growth. We 
cannot discuss this theory here; nor would it be prudent to enter 
into it in any large way. But, we may remark upon it, that, sup- 
posing Schwendener’s hypothesis were true, still, the Lichen would 
be a distinct plant, and would have a claim to be so recognised. 
Inasmuch, as the supposed fungi and algze combined, produce a plant 
differing from either of themselves, and which could not exist if 
they were separate ; also, if either the green cells, or the hypha, 
produce the one or the other, then they are no longer either algz 
or fungi; for a true alga does not grow fungal hyphee, nor does a 
true fungus produce green algal cells. But the Lichen has its own 
independent characteristics, independent either of fungi or alge. 
It has its own distinct and definite forms, its own habits of life, its 
own organs of self-propagation; and if fungi and alge were by 
some means obliterated from the earth, so far as their presence is 
concerned, Lichens would continue to flourish just the same. 
But further, most, or all our leading lichenologists are against this 
dual-hypothesis of Schwendener. This does not prove the theory 
untrue we know ; but it is a fact which carries great weight, when 
we reflect that they who have made Lichens a special and a life 
study, must be allowed to be as well or better acquainted with 
them than men whose investigations have for their object merely 
the founding or the support of a theory. Dr. Nylander, than whom 
does not live a greater authority on Lichens, by his own investiga- 
tions and from his own knowledge, has repeatedly shown the 
absurdity of Schwendener’s theory ; and he speaks of it as “ that 
hypothesis which none indeed, but tyros can patronise.” “An 
hypothesis informal and absurd, supported by no serious observa- 
tions.” As to how Lichens shall be regarded anent this hypothesis, 
Mr. Bentham considers that “ whatever be the result, the group of 
Lichens is so distinct in its negative characters, and at the same 
time so extensive and varied a one, that it seems more methodical 
to treat it, as heretofore, as a distinct class, than to absorb it in 
that of fungi, notwithstanding the close affinity shown by its repro- 
ductive organs.” In as brief a manner, as is consistent with clear- 
ness, we shall now endeavour to give some description of the 
Lichen organism, with some reference to its habits and uses ; and 
then, drop a few hints relative to the study of this group of plants. 
The Lichen, as a plant, has no axis, either ascending or descending; 
no branches or leaves, in the same sense as phenogamous plants. 
Its nearest approach to a leaf can only be called a lobed or 
laciniated frond. Its vegetative or expansive portion, is denomi- 
nated a thallus. (Gr. ¢a//os, a young shoot or frond). The 
