172 THE LIVING WORLD. 



importance. The typical vegetation of the Carboniferous became less 

 prominent and the cycads appeared. The cycads are the prominent 

 type of the Mesozoic. During the passage of the Mesozoic, however, 

 we see a change in the flora of a radical sort. Even with the Trias- 

 sic (6) the giant horse tails began to wane, and the more modern forms 

 of moderate size appeared. In the Jurassic (7) the cone-bearing plants 

 reached their highest development, from which culminating point 

 they have steadily declined. Some of our modern forms arose at this 

 time, the genus Pinus being in considerable abundance. During the 

 Jurassic also the first of the endogens made their appearance in the 

 form of screw pines and grasses, and a little later the palms appeared. 



The Cretaceous (8) period is, however, the line that marks the 

 boundary between the older vegetable world and the modern, just as 

 the beginning of the Mesozoic separated the older animals from the 

 modern forms. Occasional traces of the higher flowering plants are 

 found in the lower rocks of the Cretaceous, but it is in those of the 

 upper Cretaceous that they appear in abundance. Here there sud- 

 denly bursts upon our view an abundant flora of modern forms. 

 Most of the plants of that time belonged to the same genera as those 

 living to-day, and many of them were, so far as we can tell, of the 

 same species. Our knowledge of them is chiefly confined to the 

 preserved leaves, and these are a rather unsatisfactory basis for deter- 

 mination of species, but there seems to be no doubt that the poplars, 

 willows, beeches, oaks, birches, alders, laurels, sassafras, magnolias, 

 butternuts, hickorys, and many others were represented in profusion. 

 There is also pretty good evidence of the existence of the higher 

 flowering plants, like the Composite, at this time, though doubtless 

 the plants with inconspicuous flowers predominated. In short, at 

 this time the modern botanical world was nearly complete, so far as 

 type was concerned. Its highest forms had been developed even 

 then, and from that time to the present the growth has been simply 

 in the expansion of typesUhen existing, and in the relative increase 

 of the numbers of the highest flowering plants. The gymnosperms 

 certainly have become less abundant, and the plants with large con- 

 spicuous flowers have greatly increased in preponderance. 



The endogens have remained nearly constant since then, so that 

 we may say that in the later Cretaceous the vegetable world reached 

 nearly as high a position as it has to-day. 



We may now ask whether in this history of plants we can trace 

 the origin of the different groups of plants from each other. As 



