CLASSIFICATION' OF PLANTS. 



2. Atif/iospernis, wliicli product' true fruits enclosing 

 the seeds. In this gnnij) there are two well-marked sub- 

 divisions ditTcriii^ in the structure of the seed and stem. 

 Tlioyare the Endo<icnHyOV inside growers, with seeds hav- 

 ing one seed-leaf only, as the grasses and the j)alms ; and 

 the Krof/pus, having outside-growing woody stems, and 

 seeds with two seed-leaves. Most of the ordinary forest- 

 trees of temperate climates belong to this ^roup. 



On referring to the geological table, it will be seen 

 that there is a certain rough correspondence between the 

 order of rank of phmts and the order of their apj)earance 

 in time. The oldest plants that we certainly know are 

 Algtu, and with these there are plants apparently with 

 the structures of Thallophytes hut thj habit of trees, and 

 which, for want of a better name, I may call Protof/ens. 

 Plants akin to the Rhizocari)s also appear very early. 

 Next in order we find forests in which gigantic Ferns and 

 Lycopods and Mare's-tails predominate, and are assijciated 

 with pines. Succeeding these we have a reign of Gym- 

 nosperms, and in the later formations we find the higher 

 Plunenogams dominant. Thus there is an advance in 

 elevation and complexity along with the advance in 

 geological time, but connected with the remarkable lact 

 that in earlier times low groups attain to an elevation 

 unexampled in later times, when their places are occu- 

 pied with plants of higher type. 



It is this historical development that we have to trace 

 in the following pages, and it will be the most simple 

 and at the same time the most instructive method to 

 consider it in the order of time. 



