INTRODUCTION. XXlii 



had not travelled far, but were petrified in water near tho land 

 on which they grew. This conclusion is also supported by the 

 tendency to localisation of the types for instance, Cupressin- 

 oxylon vectensc is the commonest form in the Isle of Wight, 

 while Podocarpoxylon woburnenst is the preponderating form 

 in Woburn. Both show annual rings and both lived in similar 

 climates, and the prevalence of one or the other form probably 

 depended on local distribution, which in its turn was correlated 

 with ecological differences comparable with those which to-day 

 determine one wood as being of beech, another of oak. 



The presence of Bennettitet, which occurs not only in the 

 Isle of Wight, but also in Kent, has generally been held to 

 indicate a tropical or subtropical climate. There is, however, 

 no certainty that this was the case, and Psemlocycas (see 

 Nathorst, 1907), a genus belonging to the same family in sensu 

 lato, inhabited the Arctic at a time when, though the climate 

 was warmer than at present, it could not have been tropical. 



The large number of Abietinese in the Lower Greensand is 

 highly suggestive of a cool, if not actually a cold climate (see 

 Gothan 1908, among others, and note also the present distri- 

 bution of the Abietineae). This view is strongly supported by 

 the remarkable and total absence of Araucarinea?, a group 

 widely distributed in most European, and in the English 

 deposits in particular, both of earlier and later periods, which 

 are supposed to have been relatively warm. Araucaria itself is 

 plentiful in the Jurassic, the Wealden, and the succeeding Upper 

 Cretaceous and Tertiary of this geographical region : its remark- 

 able absence from the English Lower Greensand, particularly 

 in a flora represented so largely by petrified woods, among 

 which its woody branches would so naturally have been pre- 

 served had they been present, appears to indicate clearly that 

 the climate was temporarily too cool for it. Supporting this 

 conclusion are the well-marked growth-rings, so regular and 

 normal as to have every appearance of being annual rings (see, 

 for example, PI. Ill, fig. 1), which are present in nearly all 

 the woods described. While growth-rings in Angiosperms do 

 not necessarily indicate seasonal change of climate, in the 

 ever-green Gymnospcrms they do (see Gothan 1908, Stopes 

 1914, etc.). 



The evidence from the plants, that Aptian times in this region 



