398 



THE WONDERS OF GEOLOGY. Lect. IV. 



naturally. Similar characters are observable in the petioles 

 of the recent Zamiae ;* the presence of this characteristic 

 plant of the Wealden so high up in the chalk formation is 

 in accordance with the occurrence of bones of the Iguano- 

 don, &c. in the greensand of Kent, which we shall notice 

 hereafter. 



In the strata of Tilgate Forest, the Clathrarias are inva- 

 riably associated with waterworn 

 bones of reptiles, pebbles, gravel, 

 and other drift ; and are often 

 imbedded in the fluviatile con- 

 glomerate which is found in 

 some parts of the Wealden. They 

 Lign. 92.— a petiole of cla- appear to have floated down the 



thraria Lyellii; from the riyer with the carcasgeg an( J 



stem of the specimen figured 



Lign. 9i. limbs of the reptiles, and at 



«, The external surface; 6, the in- l en gth to have Sunk to the 



markings, left' on the summit bottom, and become imbedded in 



by the separation of the leaf. tne mU( J f tne d e lt a , 



A cluster of petioles belonging to a large plant of the 

 Clathraria, has recently been discovered in the greensand 

 near Maidstone ; in the same quarry of Kentish-rag in 

 which were found, some years since, a considerable portion 

 of the skeleton of an Iguanodon, associated with din f ted 

 coniferous wood, and other vegetable remains. I have 

 collected a few detached petioles of Clathraria from the 

 chalk marl, and white chalk, near Lewes. 



23. Fruits of conifers. — The seed-vessels of several 

 coniferous trees and plants have been discovered in the 

 Wealden, but under circumstances which render it impos- 



* In a flourishing old plant of the Encephalartus pungens from 

 South Africa, in the botanic gardens at Kew, all the lower part of the 

 stem, beneath the coronet of foliage, is covered with persistent petioles ; 

 those which have borne leaves have vascular pits on the summit, but 

 the abortive petioles are smooth and entire at the apex. 



