Section IV., 1911. [125] TRANS. R. SAC: 
Were there Climatic Zones in Devonian Time ? 
By G. F. Matruew, D.Sc., LL.D. 
(Read May 17, 1911.) 
INTRODUCTION 
As we find the world of to-day divided into regions occupied by 
varied groups of plants that have in times past adapted themselves to 
various conditions of environment, so in the past ages similar climatic 
differences no doubt existed. The Marquis of Saporta has written 
an essay on this subject which enters very fully into the evidences of 
the diversity of climates in past time and traces the condition of the 
world in this aspect from uniformity of climate in Palæozoie Time to 
the diversity which now prevails. Saporta does not seriously consider 
plants in relation to climate previous to the Carboniferous Age, but 
the inference to be drawn from his memoir is that there was no diversity 
in or previous to the Carboniferous Age, and of this he writes as follows: 
—“Pause a moment before leaving the Carboniferous flora to consider 
. that there prevailed then in all the modern zones from temperate 
to glacial a perfectly equal temperature, and a climate of which the 
tepid humidity cannot be questioned . . . The equality of climate 
was so complete that the Vegetable Kingdom itself was incomplete. 
In place of four groups it contained only two and these two are just 
those that have now the fewest species, perhaps ten times less than the 
two others . . . These two classes were the Vascular Cryptogams 
and the Gymnosperms. ”* 
The writer of the memoir then goes on to ask when did this blank 
[equality] disappear?, and states that it was a progressive change 
through the Trias, Rhetic, Jurassic, &e., ages, until it culminated in the 
excessive contrasts of the Pleistocene and Recent times. 
In this view of the evidence to be draws from the ancient floras 
Saporta is supported by Professor R. Zeiller, who in discussing the 
Carboniferous plants of the coal basin of Tete in South Africa remarks 
on their resemblance to the Upper Carboniferous of Europe, and suggests 
that they show the prevalence of a quite uniform climate through all 
the terrestrial zones. 
It was formerly supposed that the great heat of the earth in its 
earlier Palæozoic ages would have produced the uniformity of climate 
which it has been claimed has been found to have prevailed in Carbon- 
*These two classes of Saporta are now really three, for out of his first has been 
taken the Class of Pteridosperms. 
