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 Cycadese 

 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 csenoHthic, or 

 tertiary period, and we arrive thus at the consideration of 

 the sixth and last class of the vegetable kingdom, that of 

 the Metaspevmce, Angiospermce, 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 

 two classes into which the main class of Angiosperms is 

 generally divided, namely, the one seed-lohed plants, or 

 monocotylce, and the two seed-lohed plants, or dicotylce. 

 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 Monocotylse, whilst others consider 

 them as Gymnosperms. In regard to the two classes of 



* The primary stock of the Coniferae divided into two branches at an early 

 period, into the ArancariaB on the one hand, and the Taxaceee, or yew-trees, 

 on the other. The majority of recent Coniferae are derived from the former. 

 Out of the latter the third class of the Gymnosperms — the Meningos, or 

 Gnetaceae — were developed. This small bnt very interesting class contains 

 only three diflferent genera — Gnetam, Welwitschia, and Ephedra ; it is, 

 however, of great importance, as it forms the transition group from the 

 Coniferae to the Angiosperms, and more especially to the Dicotyledons. 



