the next era, where they gave place to the true horsetails, a much 
more lowly type, but perhaps better fitted to cope with the chang- 
ing conditions of the long stretch of time between then and now. 
Ferns were more abundant than ever, running riot in variety of 
form and adaptability. The same was true of their near relatives, 
the curious cycad-like ferns which bore seed-like structures. 
Moreover, representatives of true cycads (sago palms) appeared. 
The forests of Cordaites gave place to still higher types of con- 
ifers, some of which had foliage similar to our present-day yews. 
Others were probably ancestors of the temple conifer, ( Ginkgo) 
the curious maiden-hair tree, which escaped extinction from our 
present flora, only because it found favor in the eyes of an 
oriental priesthood!. 
The closing of the Paleozoic era marked the doom of the 
club-mosses, selaginellas, horsetails and their relatives as a domi- 
nating element of the earth’s flora. In the coal period they had 
reached their millenium, both in grandeur and variety of form 
and in number of individuals. Henceforth to the present time, 
their history has been one of increasing insignificance. Today 
they are represented by a few very modest, inconspicuous types 
such as the ground pines of our northern forests, the selaginellas 
or little club-mosses so common as ground carpets in tropical 
forests at certain elevations, and the scouring rushes (horsetails), 
inhabitants especially of low swampy regions and of railroad 
embankments. This latter group in some forms still reaches a 
fair height, 15-20 feet, and in a few regions, they are still locally a 
large element of the vegetation, — relics of the past, much as are 
the redwoods of the Pacific coast, a group of plants once common 
over the whole world from Greenland to Australia. 
Contrasted with the tranquil Paleozoic, the next era, the 
Mesozoic, is an age of marvellous activity and change, with a 
climate for the most part mild and seasonless. Climatic zones 
slowly put in their appearance as the age progressed toward its 
close. These zonal differences in temperature were probably slight 
at first, and more noticeable on the sea, the Arctic waters being- 
cooler. Mountain making took place on a grand scale and volcanic 
activity, especially near the close of the era, must have presented 
scenes rivaling those once claimed for Gehenna, the old-time 
biblical hades. The result of all this turmoil and change lies be- 
fore us today as the Cascades, Sierra Nevadas and the Rockies. 
Animal life also seemed to be outdoing itself, especially in an 
effort toward grotesqueness in form and gigantic proportions. 
Reptiles of innumerable shapes and sizes walked and crawled 
over the land, swam the seas and filled the air with their whirring 
wings, some of which had a spread of twenty feet. Seas and 
rivers swarmed with crocodiles and huge turtles. Winged 
dragons with bird-like heads and teeth-filled jaws were no super- 
stition in those days, nor were the mountains of flesh and bone, 
50-70 feet long, which took the form of plant- and animal-eating 
dinosaurs,— animals, the largest the world has ever known. Birds 
were uncommon almost to the end of the era, while mammals 
(animals which suckle their young, such as. are most of our 
present-day land animals) were small, few and insignificant. 
The plants of such a world were no less marvellous, especially 
toward the latter half of the era, when representatives of our 
modern flowering plants appeared. In the first part of the era, 
ferns became less abundant and resembled many of our tropical 
forms of today. The club-mosses were much simpler and largely 
stragglers, while true horsetails, in canebrake-like thickets 
occupied the margins of the swamps, inland lakes and seas, in 
place of the calamites of the age just passed. Cycads were so 
