296 ~ ‘ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
atmospheric blanket and retainer of the sun’s heat rays. Therefore 
they hold that these factors alone were sufficient to have brought on a 
glacial climate. It may be that this theory will not stand the test of 
time, but even so we have learned that in Carbonic times there were 
earth movements on so grand a scale as to be but slightly inferior to 
those of the late Tertiary that were followed by the Pleistocene 
glacial climate. 
Permic.—Very early in Permic time the mild climate of the past 
was greatly changed; the evidence is now overwhelming that through- 
out the Southern Hemisphere there was a glacial period seemingly 
of even greater extent than that of the Northern Hemisphere during 
the Pleistocene. This evidence is most easily seen in the wide dis- 
tribution of the tillites and the scratched and polished grounds over 
which the land ice moved in Africa, Australia, Tasmania, India, and 
South America. In the Northern Hemisphere the evidence of ice 
work is far less marked; but tillites occur near Boston, Massachusetts, 
and in the Urals, and there is much evidence of thin and arid climates, 
seen in the widely distributed red formations. Then, too, the land 
life of this time clearly indicates that a great climatic change had 
taken place in the environment of the organic world. 
The grand cosmopolitan swamp floras of the Upper Carbonic, con- 
sisting in the main of spore-bearing plants, such as the rushes (Kqui- 
setales), the running pines, and clubmosses (Lycopodiales), and the 
ferns, among which were also many broad-leaved evergreens (Cor- 
-daitales) and seed-bearing ferns (Cycadofilicales), were very largely 
exterminated in the Southern Hemisphere at the beginning of Permic 
time. In the Northern Hemisphere, however, the older flora main- 
tained itself for a while longer, as best seen in North America, but 
finally the full effects of the cooled and glacial climates were felt 
everywhere. Then in later Permic time the old floras completely 
vanished, except the hardier pecopterids, cycads, and conifers of the 
Northern Hemisphere, and with these latter mingled the migrants 
from the hardy Gangamopteris flora originating in the glacial climate 
of the Southern Hemisphere. (White, 1907.) Some of the trees 
show distinct annual growth rings, and hence the presence of winters. 
It was these woody floras that gave rise to the cosmopolitan floras 
of early Mesozoic time. 
With the vanishing of the cosmopolitan coal floras also went nearly 
all of the Paleozoic insect world of large size and direct development, 
for the insects of late Permic time were small and prophetic of modern 
forms. Then, too, they all passed through a metamorphic stage 
indicating, according to Handlirsch, that the insects of earlier Permic 
time had learned how to hibernate through the winters in the newly 
originated larval conditions. 
