8 OUTLINE OF PLANT GEOGRAPHY 



sometimes separated as a distinct class — (Psilophyta). The 

 oldest and simplest of these, the Rhyniaceae, show some very in- 

 teresting resemblances to certain existing bryophytes, and support 

 the theory that the vascular plants have come from some such 

 bryophytic ancestors. 



The later Devonian formations show the beginnings of the 

 different classes of ferns, horsetails and club-mosses, which 

 constitute the Pteridophytes of the present day; bub there were 

 also found in the latest Devonian certain types of seed-bearing 

 plants as well, the Cordaitales, which, however, completely dis- 

 appear before the end of the Palaeozoic. 



The various plant types of the late Devonian continue into the 

 Carboniferous where they are supplemented by a great assembly 

 of other related forms which have been preserved in a very perfect 

 state in immense numbers, so that we can make a pretty accurate 

 estimate of the vegetation of the great coal period. 



This flora during much of the Carboniferous was practically 

 world wide in its distribution, and indicates a mild excessively 

 humid climate, such as now exists in the mountain rain-forests 

 of the tropics, and in some temperate regions like parts of New 

 Zealand, where pteridophytes play a very important role in the 

 vegetation. 



Ferns, horsetails and club-mosses abounded, the two latter 

 classes having genera which attained tree-like dimensions and 

 were much better developed than their degenerate modern repre- 

 sentatives. Among tree-ferns and club-mosses were seed bearing 

 types, the Cordaitales, beginning at the end of the Devonian, 

 which flourished in the Carboniferous. All of these Palaeozoic 

 seed -plants disappear before the next great geological epoch — 

 the Mesozoic — and their place is taken by forms related to exist- 

 ing ones and which first appear in the Permian. 



The latter part of the Carboniferous and the succeeding Permian 

 era show evidences of a decided cooling off, extensive glaciers 

 existing, especially in the southern hemisphere. At this time, 

 the land-masses of the southern hemisphere appear to have been 

 in more or less intimate connection, and this "Gondwana Land," 

 was quite separate from the northern land masses, and in it was 

 developed a peculiar flora " Glossopteris flora" which was supposed 

 to be a cold-climate one, and supplanted the earlier Carboniferous 



