PALEOBOTANY — BERRY. 381 



The Devonian Arthrophytes included numerous primitive forms 

 of Calamites known as Archaeocalamites. These are distinguished 

 from the later Calamites by their unequal internodes, nonalternating 

 ribs, and their dichotomously divided leaves. The imperfectly known 

 order Pseudoborniales, with their lax cones and similarly compound 

 leaves, belong here. Foliage indistinguishable from that of the later 

 Asterophyllites and Annularia was present in the Devonian. Spheno- 

 phyllum — theoretically the most ancient Arthrophyte — was present 

 in North America, Europe, and Bear Island, and the genus Hyenia 

 from the Devonian of Norway is also supposed to have represented 

 the Sphenophyllales. 



The higher vascular plants of the phylum Coniferophyta were un- 

 doubtedly present during the Devonian, but so much of the material 

 is made up of fragmentary impressions that great confusion prevails. 

 Forms called Psygmophyllum may represent either the Ginkgoales, 

 Cordaitales, or be simply fern foliage. A Ginkgoplryllum described 

 from the Devonian of Ireland appears to be an early member of the 

 Ginkgo stock. The Cordaitales, which were so prominent in the later 

 Paleozoic, are represented in the Devonian by pith casts resembling 

 Artisia and Sternbergia. This is not certain proof of the presence of 

 true Cordaites nor are the fragments from Devonian rocks referred to 

 Cordaites conclusive. The decisive evidence of the presence of Cor- 

 daites or of closely allied forms belonging to this order, is furnished 

 by the petrified woods from widely scattered Devonian localities re- 

 ferred to Dadoxylon or Araucarioxylon. A recently proposed genus, 

 Callixylon, is based upon beautifully petrified wood of several species 

 from the Middle and Upper Devonian of Ohio and Russia. 



CARBONIFEROUS AND PERMIAN COSMOPOLITAN FLORAS. 



The Carboniferous rocks contain very many seams of coal, and in 

 the Northern Hemisphere, at least, the Carboniferous is thought of 

 as preeminently the period of coal formation. The enormous quan- 

 tity of vegetable debris necessaiw for the formation of even a single 

 coal bed has led to the belief that the vegetation of Carboniferous 

 times was ranker and more luxuriant than at any other time in the 

 earth's history, and that it grew in enormous swamps under torrid 

 cloudy climatic conditions. Nothing is farther from the truth. 



The vegetation of the Carboniferous was probably not more varied 

 or luxuriant than at many other times in geological history, and it 

 is doubtful if the palustrine forests of Carboniferous or Permian 

 times were as dense, and they certainly contained much less of a 

 variety than the existing tropical rain-forests or jungles, such as, 

 for example, that of the Amazon basin. What makes the Car- 

 boniferous forests so interesting to the geologist quite aside from 



