conifers preceded the cycads, and as early as the 

 Carboniferous age formed as prominent an object in 

 the landscape as they do now. The late Hugh Miller 

 found one in the lower division of the Old Eed Sand- 

 stone, near the town of Cromarty. They increased 

 greatly towards the close of the paloaozoic age, both in 

 genera and species. The dicecious Taxinian branch 

 of this Order has been met with in the Calciferous 

 Sandstones of Edinburgh — a Lower Carboniferous for- 

 mation — also the stem and spike of an Aroid. Cryp- 

 tograms of higher organization than their present 

 congeners clothed the lower levels of the land at this 

 period, while Stigmaria and Sigillaria, which had 

 hitherto formed so important a feature in the palaso- 

 zoic vegetation, began to decline, and entirely dis- 

 appeared before the secondary period was usheied in. 

 At this time of the earth's history the first cycad 

 appeared, accompanied by new forms of conifers 

 equiseta3 and ferns, which began to cover the heights 

 of the newly emerged land, giving quite a new aspect 

 to the flora. No true o;rass is known to have lived at 

 this period. New forms of cycads successively 

 appeared, and became more and more numerous 

 during the latter part of the ]3ermian age ; during the 

 oolitic age tliey reached their maximmn in England, 

 and probably also over the whole globe. After the 

 wcalden period they showed symptoms of decline, and 

 from that time, although perhaps slowly, receded step 

 by step, leaving no traces of their existence for long 

 periods. The cretaceous age was properly the closing 



