352 Count Gaston de Saporta on the Temperature 



evolution has rather been successive ; that is to say, certain 

 sections have preceded others which have come more slowly 

 upon our ground : this more or less regular progress consists in 

 a sort of elaboration in which the notion of specific individuality 

 is much weakened. In the genera with a fixed physiognomy 

 this notion disappears still more ; so that in vegetable palaeonto- 

 logy everything concurs to increase the importance of the type 

 to the detriment of the species, since the former does not cease 

 to manifest its action during a very long period, whilst the spe- 

 cies issuing from this type resemble each other, notwithstanding 

 the diversity of the epochs to which they belong, to such a de- 

 gree that they are sometimes not very distinguishable. 



In Palaeozoic times the heat may have been greater than it is 

 now even under the equator; nevertheless we have no direct 

 proof of this by means of plants, since the number of arborescent 

 ferns has been found to be less than was at first supposed. We 

 know only that the temperature of the terrestrial surface was 

 then more uniform, more equable than at present ; and that the 

 polar regions themselves, participating in this uniformity, pos- 

 sessed plants like those of other countries. 



This is a noteworthy fact, but one the importance of which 

 must not be exaggerated, since the same fact existed again to- 

 wards the Miocene period. The polar forms of the Carboniferous 

 formation, which, in part at least, are specifically distinct from 

 those of other contemporaneous regions, may have been capable 

 of supporting a temperature relatively colder than that which 

 governed the coal-vegetation of the rest of the world. It is 

 therefore by no means impossible to conceive a certain gradation 

 of climates in this primitive period. 



The absence of any classes of plants except the Cryptogamia 

 and the Gymnospermia cannot be an argument in favour of an 

 excessive elevation of temperature during this primitive age, 

 since the organic development from which the vegetable king- 

 dom has issued has operated in a gradual and determinate order, 

 which, so to speak, implies the anteriority of certain classes. 

 This anteriority must have depended at least as much on the 

 mode of evolution proper to the vegetable kingdom as on the 

 degree of elevation of the initial temperature. The most we can 

 say is, that, organisms having been in all times adapted to the 

 external circumstances in the midst of which they are produced, 

 we may deduce, by analogy, from the examination of these or- 

 ganisms the determination of the circumstances themselves; 

 and it is in fact at this point that we must stop. 



Whatever may have been the initial elevation of the tempera- 

 ture, the data that we obtain from fossil botany for the Coal period 

 are reduced to the following, namely, its greater uniformity, its 



