644 



GEOLOGY. 



the opening of the period, and gradually increased in prevalence, while 

 the residual Carboniferous species declined. The general aspect of 



Fig. 296. — A verticel of leaves of Ulossopteris. X2. (After Etheridge.) 



the flora remained, however, that of poverty. Two new types of 

 much interest came in and became characteristic, Walchia and Voltzia. 

 Walchia (Fig. 297) resembled an Araucarian conifer in its foliage, 

 but its seed organs were apparently different. While conifers have 



Fig. 297. — Walchia piriformis, a Permian conifer of Europe. 



been reported from earlier systems on the doubtful basis of woody 

 tissue, Walchia may probably be safely regarded as representing them. 



