of Geological Periods, 273- 



by this celebrated author, that the difference between the ex- 

 treme seasons is much more strongly marked in Europe than in 

 Australia, and the climate is less uniform even within the limits 

 of each season*. At Dusky Bay, in New Zealand, according to 

 Dr. Hooker, arborescent ferns grow under a latitude of 46° 8' ; 

 and in the Auckland and Campbell Islands they are met with 

 as far as 53°. 



It can no longer be asserted that the temperature of the 

 tropics is necessary for the existence of these plants ; and there- 

 fore it is not to their presence alone that we can appeal for the 

 admission of a high temperature during this first epoch, but 

 must rather consider the general character of the vegetation. 

 The types of this age, of which there still exist som.e re- 

 presentatives, diminished in size and generically distinct — the 

 Lycopodiacese and Equisetacese — as well as the ferns themselves_, 

 flourish nowhere so much as within the tropics; and it cannot 

 be denied that this neighbourhood is favourable to them, as 

 their number, dimensions, and comparative importance increase 

 in proportion as we advance in this direction. It is from the 

 combination of these indications that we must believe in the 

 existence during this first period of a warm temperature, a dense 

 and cloudy atmosphere, and a permanent and tepid moisture. 



The continents were then but slightly varied in surface- 

 features {accidentes) ; the flow of water on the surface of the soil 

 gave rise neither to rivers nor torrents, but to lagoons fed by a 

 multitude of brooks which descended from all the slopes and 

 traversed the bottom of the undulations, as we still see in granitic 

 countries, which, better than any others, have retained the fea- 

 tures of this ancient configuration of the surface of the earth. 

 But the vegetation of the Carboniferous period has been pictured 

 too often to render it necessary for us to dwell longer upon it. 



On penetrating into the Trias, we meet with the genus Equi^ 

 setum, still difi'used throughout all latitudes, although its species 

 now, even in hot countries, are far from attaining the dimen- 

 sions of its ancient forms". In fact Equisetum arundinaceum 

 (Bory), from the shores of the Mississippi, one of the largest of 

 the group, does not approach E. arenaceum (Ilcer), from the 

 Keuper, or even equal some Tertiary species. 



In the Jurassic epoch is developed the group of the European 

 Cycadese, probably generically distinct from those of the present 

 day ; it is, however, to the Cycadea) growing in the southern parts 

 of the eastern hemisphere, such as Dioiij Macrozaniia, and Ence- 



* At Hobart Town the hibernal and eestival means are represented by 

 5°G and \7°"2 C, whilst at Rome, about 1 degree further from the equator, 

 the annual temperature being 13'''3 C, tlie hil)ernal mean descends to S°, 

 and the ccstival reaches 30° G. 



