Dr Martius on Antediluvian Hants, 49 
vast ruin of primeval times ; others are found in countries 
very remote from their original one, or from those in which 
similar plants now grow, thus shewing that the heat has been 
much greater in former times. For this reason, I directed my 
attention, on a journey made by me through Brazil, toward the 
investigation of those forms of plants, which might be consider- 
ed as prototypes of the antediluvian vegetables discovered in 
our own countries ; nor have my efforts been altogether without 
success, as some things occurred to me capable of throwing 
light upon the nature of antediluvian plants, and which I now 
proceed to announce. 
The tree-ferns,, which constitute so beautiful a feature of the 
tropical regions, exhibit several characters by which they may 
be compared with the ancient plants ; but as they have been 
seen but by few botanists, and their structure is consequently 
very little known, they can scarcely afford us much assistance in 
our efforts to discover the nature of the vegetables dug up from 
our coal-mines. Indeed, when I saw the first specimens of 
Polypodium corcovadense^ so remarkable for the tesselated sur- 
face of its caudex, 1 was not only struck by the novelty of the 
circumstance, but immediately called to mind the figures of 
certain petrified forms described by Sternbergs under the name 
of Lepidodendron ; on comparing which, after I had returned, 
with the stems of eight arborescent species collected upon my 
journey, I found them connected by so intimate an affinity, that 
I could entertain no doubts of their generic identity ; and I trust 
I shall be able to shew that their characters are in perfect accor- 
dance. 
The caudex or stem of arborescent ferns is fixed into the 
earth by roots, which are small in proportion to the size of the 
plant, short, and branched : it is straight, scarcely ever flexuose, 
unless in the weaker species, rising, somewhat attenuated up- 
wards, from the base, which is often invested with long sub- 
simple fibres running down upon the root, to a height varying 
from 6 to 25 feet, shaded by terminal fronds, perpetually shoot- 
ing up from the apex of the stem by a sort of renovation, the 
former fronds decaying, and giving place to a more beautiful 
covering : The fronds arise from the stem in spiral order, some- 
VOL. XII. NO. 23. JANUARY 1825. 
D 
