yster. And yet Goldsmith was engaged on his work
little more than eighty years ago. In fine, the true principles of
classification in the animal kingdom are of well nigh as recent
development as geologic science itself, and not greatly more ancient in
even the _vegetable_ kingdom. It would, of course, be wholly out of
place to attempt giving a minute history here of the progress of
arrangement in either department; but it can scarce be held that the
natural system of plants was other than very incomplete previous to
1789, when Jussieu first enunciated his scheme of classification; nor
did it receive its later improvements until so late as 1846, when, after
the publication, in succession, of the schemes of De Candolle and
Endlicher, Lindley communicated his finished system to the world. And
there certainly existed no even tolerably perfect system of zoology
until 1816, when the "Animal Kingdom" of Cuvier appeared. Later
naturalists,--such as Agassiz, in his own special department, the
history of fishes, and Professor Owen in the invertebrate
divisions,--have improved on the classification of even the great
Frenchman; but for purposes of comparison between the scheme developed
in geologic history and that at length elaborated by the human mind, the
system of Cuvier will be found, for at least our present purpose,
sufficiently complete. And in tracing through time the course of the
vegetable kingdom, let us adopt, as our standard to measure it by, the
system of Lindley.

Commencing at the bottom of the scale, we find the Thallogens, or
flowerless plants which lack proper stems and leaves,--a class which
includes all the algae. Next succeed the Acrogens, or flowerless plants
that possess both stems and leaves,--such as the ferns and their allies.
Next, omitting an inconspicuous class, represented by but a few
parasitical plants incapable of preservation as fossils, come the
Endogens,--monocotyledonous flowering plants, that include the
palms, the liliaceae, and several other families, all characterized
by the parallel venation of their leaves. Next, omitting another
inconspicuous tribe, there follows a very important class,--the
Gymnogens,--polycotyledonous trees, represented by the conifers; and
cycadaceae. And, last of all, come the Dicotyledonous Exogens,--a class
to which all our fruit, and what are known as our "forest trees,"
belong, with a vastly preponderating majority of the herbs and flowers
that impart fertility