FLORA. 219 
He proceeds to specify coincidences, such as the contem- 
poraneous appearance in Greenland and in the Carpathian 
Mountains, separating Bohemia and Hungary, of the same 
characteristic types of cycas-like plants. Older forms of 
ferns seemed to die out; but of those which now appeared 
their representatives must be sought in the present day in 
the vicinity of the tropics, or in the warmer parts of the 
temperate zones of the northern and southern hemispheres. 
Thirteen species of Gleichenia have been identified by 
Professor Heer as similar to those growing at the same 
time in other parts of Europe. The Glerchenias of the 
present day are diffused over the tropics and the islands 
of the South Sea. But one species, bearing fronds once 
or repeatedly divided dichotomously, and generally pro- 
vided with a bud situated between the branches of the 
dichotomous division, has advanced so far north as Japan. 
And the Polar Gieichenias, which present a physiognomy 
absolutely the same, must have sought the same conditions 
of warmth and humidity as their congeners of the present 
day. 
‘The conifers of this epoch divide themselves naturally 
under several categories, having each its peculiar signifi- 
cation. It is beyond contradiction the most important 
group of the period now under consideration ; and amongst 
the types comprised in it may be remarked many which 
show themselves for the first time, and of which it seems 
that the cradle should decidedly be placed in the interior 
of the Arctic zone. It is there that these types, after 
having remained a long time confined to it, and after 
having there given rise to a certain number of forms, went 
out to spread themselves further towards the south in 
distinct rays, some later, in such a way as to gain access 
to the two continents, and there to make good their 
footing, and maintain it, a long time after they had dis- 
appeared from the Mnd of their origin. 
‘We have spoken of the Salisburias—they continue to 
show themselves always divided into two groups, that of 
