and beauty to our gardens and meadows. This last
class, though but one, now occupies much greater space in the vegetable
kingdom than all the others united.

Such is the arrangement of Lindley, or rather an arrangement the slow
growth of ages, to which this distinguished botanist has given the last
finishing touches. And let us now mark how closely it resembles the
geologic arrangement as developed in the successive stages of the
earth's history.

[Illustration: Fig. 1.[4]

-+-------------------------
| Thallogens.
Silurian. |
| Acrogens.
-+-----+-------------------
| | | Gymnogens.
Old Red. | | |
| | |
-+-----+-----+-------------
| | | | Monocotyledons.
Carboniferous. | | | |
| | | |
-+-----+-----+-----+-------
Permian. | | | |
-+-----+-----+-----+-------
Triassic. | | | |
-+-----+-----+-----+-------
| | | | : Dicotyledons.
Oolitic. | | | | :
| | | | |
-+-----+-----+-----+-----+-
| | | | |
Cretaceous. | | | | |
| | | | |
-+-----+-----+-----+-----+- Dicotyledonous Trees.
| | | | |
Tertiary. | | | | |
| | | | |
-+-----+-----+-----+-----+-
Geologic [Thal. Ac. Gy. Mon. Dic.] arrangement.
Lindley's [Thal. Ac. Mon. Gy. Dic.] arrangement.

THE GENEALOGY OF PLANTS.]

The most ancient period of whose organisms any trace remains in the
rocks seems to have been, prevailingly at least, a period of
Thallogens. We must, of course, take into account the fact, that it has
yielded no land plants, and that the sea is everywhere now, as of old,
the great habitat of the algae,--one of the four great orders into which
the Thallogens are divided. There appear no traces of a terrestrial
vegetation until we reach the uppermost beds of the Upper Silurian
Sys