7 
no real evidence that a tropical climate was essential to 
their development. Houseleek and many other hardy plants 
are equally as succulent as the Cactaceae ; and neither 
palms nor tree ferns are exclusively tropical, though 
abounding at the present day in such countries. We may 
adduce the Date palm, Phcenix dactylifera, which is cul- 
tivated in Sicily, and even at Bordighiera, in Liguria ; the 
Palmetto, Chamaarops humilis, found as far north as Nice; 
the New Zealand Areca, which is seen in many places 
where the around is sometimes covered with snow for several 
days; or the Palma Magellanica, which, according to Hum- 
boldt, has been seen in 53° S. latitude ; and the gigantic wax 
palm of the Andes, Ceroxylon, which rears its lofty head 
in climates too inhospitable for any other palm, among the 
snow-clad summits of Tolima, San Juan, and Quindiu, at 
an elevation of 8,700 feet, 6,000 feet higher than palms 
are usually met with. And as for Tree Ferns, which are of 
rare occurrence in a fossil state, we find them in New 
Zealand, and on the South side of Van Diemen's Land, 
where the mean temperature little exceeds 54° of Fahrenheit. 
So that, from these instances, we have sufficient proof that 
no evidence of a satisfactory character can be derived from 
the fossil flora, indicating a tropical climate, or one materially 
differing from that of the present day."* If, indeed, any theory 
is strengthened by the facts which fossil botany presents, it is 
that of equability of temperature. The excess of watery 
surface, which it is demonstrable at one time existed, would 
very much tend to equalise the temperature of the islands, 
which, it is presumed, were emerging from the bosom of the 
deep. And, although the evidence is not yet complete, the 
theory of more equable temperature receives some confirma- 
tion from what has been already adduced ; — that the coal 
floras not only of North America and Europe are for the 
* Penny Cyclopaedia, vol. vii., p. 295. 
