46 REVIEWS. 



mate, as if each plant individually were a sort of natural thermometer. 

 This incorrect notion has been perhaps chiefly mischievous in reference to 

 the obscure regions of fossil Botany, where certain climates have been 

 hastily assumed to have existed in certain localities at a former epoch be- 

 cause certain forms are found fossilized in the strata. Thus, because Za- 

 raias are now found at the Cape of Good Hope, in New Holland, and in the 

 table-land of Mexico ; and because fossils of kindred structure are embedded 

 in the strata of England, and of other northern countries, it has been as- 

 sumed that the England of the Zamian era must have had a similarly hot 

 and dry climate to that of South Africa, or of Western Australia, where 

 these forms of vegetation are now common. The inference is, however, a 

 very vague one, resting on a very narrow basis, as will be evident when we 

 examine a little more carefully the climates where the Cycadeae are now 

 found. We shall then discover that though none inhabit a very cold 

 country, yet the range of climate, especially as regards humidity, over 

 which the Order is distributed is very extensive, some species growing 

 in the moist jungles of tropical India, others in the low islands of the Pa- 

 cific archipelagos, besides those more familiar forms which we have from 

 the arid regions of the Cape and Australia. It would be impossible to 

 tell from the mere inspection of a modem Cycadeous stem and foliage 

 whether they had grown in a tropical or extra-tropical climate ; and it must 

 be just as hazardous to pronounce on the nature of the climate which nou- 

 rished Cycadeae in the earlier eras of our planet. It would be as reason- 

 able to judge from the finding of fossil acorns or oak logs that such indi- 

 cated a climate in the regions where they occurred similar to that of modern 

 England, of which the oak may be taken as a characteristic tree. But in 

 this hasty assumption we should t,lose sight of the fact that the genus 

 Quercus has a wide distribution in tropical as well as intemperate and cold 

 latitudes, species being found from very high latitudes on the American 

 continent nearly to the equator, and occurring on the mountains and table- 

 lands of tropical India, and of the island of Java. Were the species of oak 

 now existing in Java fossilized there, leaving no descendants, some future 

 geologist, knowing the oak only as a form of vegetation of cold or tempe- 

 rate regions, might draw, from its presence in the strata of Java, a very 

 false inference respecting the early climate of that tropical island. 



That a plant does not indicate a particular climate in a manner analo- 

 gous to a thermometer or hygrometer must be evident to any one at all 

 acquainted with the powers of endurance which certain species display, and 

 the feebleness of endurance equally obvious in other species ; so that each 



