EELATIVE GEOLOGICAL ANTIQUITY OF TREES. 137 



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

 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 Eed 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 Hot so abundant, and less gigantic in their growth ; and, 

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

 and Cycadacese, 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 Cycadacese 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 superseded by the Palm, a plant which is related to them but 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 Cycadacese, 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 hiUs, or elevated 

 Mnds of the islands, which were probably wooded to their 

 summit, whilst the Cycadacese, 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 Wilhws I 

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



