ANGIOSPERMS, III 
secondary period, that of the Trias. At that time mighty 
coniferous trees—with but proportionately few genera and 
species, but standing together in immense masses of indivi- 
duals—formed the principal part of the mesolithic forests. 
This fact justifies us in calling the secondary period the 
“era of the pine forests,” although the remains of Cycadez 
predominate over those of coniferous trees in the Jura 
period.* 
From the pine forests of the mesolithic, or secondary 
period, we pass on into the leafy forests of the czenolithic, or 
tertiary period, and we arrive thus at the consideration of 
the sixth and last class of the vegctable kingdom, that of 
the Metasperme, Angiosperme, or plants with enclosed 
seeds. The first certain and undoubted fossils of plants 
with enclosed seeds are found in the strata of the chalk 
system, and indeed we here find, side by side, remains of the 
&wo classes into which the main class of Angiosperms is 
generally divided, namely, the one seed-lobed plants, or 
monocotyle, and the two seed-lobed plants, or dicotyla. 
However, the whole group probably originated at an earlier 
period during the Trias. For we know of a number of 
doubtful and not accurately definable fossil remains of 
plants from the Oolitic and Trias (sic) periods, which some 
botanists consider to be Monocotyle, whilst others consider 
them as Gymnosperms. In regard to the two classes of 
* The primary stock of the Coniferze divided into two branches at an early 
period, into the Araucariz on the one hand, and the Taxaceex, or yew-trees. 
on the other. The majority of recent Coniferz are derived from the former. 
Out of the latter the third class of the Gymnosperms—the Meningos, or 
Gnetaceze—were developed. This small but very interesting class contains 
only three different genera—Gnetum, Welwitschia, and Ephedra; it is, 
however, of great importance, as it forms the transition group from the 
Coniferze to the Angiosperms, and more especially to the Dicotyledons. 
