EELATIVE GEOLOGICAL ANTIQUITY OF TREES. 137 



the impression of the feet of the wading birds in the New Red 

 Sandstone of Connecticut. These impressions are some of 

 them eighteen inches in length and five feet apart, so that 

 the birds making them must have far exceeded in size the 

 largest African ostrich. All traces of mammalia are totally 

 absent from, the New Bed Sandstone, the Muschelchalk, and 

 Keuper, and are first found in the slates of Stone fields, in 

 the upper stages of the Oolitic formations. 



The plants found in the Secondary rocks must be regarded 

 as a flora intermediate between the plants of the Palaeozoic 

 rocks and the Tertiary formation. Ferns and club-mosses 

 are not so abundant, and less gigantic in their growth ; and, 

 in addition to these, we meet with a great number of Coniferaa 

 and Cycadaceae, or plants allied to the Cicas revoluta, or Sago 

 Palm, which is a common though somewhat costly ornament 

 of the conservatory. The stems of the Cycadaceae reached at 

 this time a height of from four to thirty-six feet, for stems as 

 long as that have been found ; but at present three feet is the 

 maximum length of the stems of. these plants, which are not 

 so numerous as formerly, as they have been to some extent 

 superseded by the Palm, a plant which is related to them but 

 far more highly organized. 



We have clear proof, from vegetable remains found in the 

 Lias and Oolitic rocks, of a landscape diversified by hills and 

 valleys. The remains of Pine-trees, which usually develop 

 on a dry, poor soil, are found, along with the fruit and leaves 

 of Zamias plants belonging to the Cycadaceae, which require 

 moisture and heat in order to grow, by which we are forcibly 

 reminded of a hilly if not mountainous landscape within the 

 tropics. The Pines would grow on the hills, or elevated 

 lands of the islands, which were probably wooded to their 

 summit, whilst the Cycadaceae, the ferns, club-mosses, and 

 horse-tails, would grow on the low lands which surrounded 

 them. 



In the Chalk rocks especially are the vegetable remains 



interesting. We find here the remains of plants with true 



leaves, and the first trees of this kind turn out to be Willows ! 



which it is well known will develop in a poor soil provided 



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