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CHAPTER VIII
SYSTEMATIC
I. CLASSIFICATION
A. WORK OF SUCCESSIVE SYSTEMATISTS
SINCE the time when lichens were first recognized as a separate class
as members of the genus Lichen by Tournefort 1 or as "Musco-fungi"
by
Morison 2
, many
schemes of classification have been outlined, and the
history of the science of lichenology, as we have seen, is a record of attempts
to understand their puzzling structure, and to express that understanding
by relating them to each other and to allied classes of plants. The great
diversity of opinion in regard to their affinities is directly due to their
composite nature.
a. DILLENIUS AND LINNAEUS. The first systematists were chiefly im-
pressed by their likeness to mosses, hepatics or algae. Dillenius* in the
Historia Muscorum grouped them under the moss genera: IV. Usnea,
V. Coralloides and VI. Lichenoides. Linnaeus 4 classified them among algae
under the general name Lichen, dividing them into eight orders based on
thalline characters in all but one instance, the second order being distin-
guished from the first by bearing scutellae. The British botanists of the
latter part of the eighteenth century Hudson, Lightfoot and others were
content to follow Linnaeus and in general adopted his arrangement.
b. ACHARIUS. Early in the nineteenth century Acharius, the Swedish
Lichenologist, worked a revolution in the classification of lichens. He gave
first place to the form of the thallus, but he also noted the fundamental
differences in fruit-formation: his new system appeared in the Methodus
Lichenum 5 with an introduction explaining the terms he had introduced,
many of them in use to this day.
Diagnoses of twenty-three genera are given with their included species.
The work was further extended and emended in Lichenographia Uni-
versalis* and in the Synopsis Lichenum 1 . In his final arrangement the
family "Lichenes" is divided into four classes, three of which are characterized
solely by apothecial characters; the fourth class has no apothecia.
They
are as follows :
Class I. Idiothalami with three orders, Homogenei, Heterogenei and Hyperogenei :
the apothecia differ in texture and colouration from the thallus: Lecidea, Opegrapha,
Gyrophora, etc.
Class II. Coenothalami, with three orders, Phymaloidei, Discoidei and Cephaloidei.
1
Tournefort 1694.
2 Morison 1699.
3 Dillenius 1741.
4
Linnaeus 1753.
6 Acharius 1803.
6 Acharius 1810.
7 Acharius 1814.