1 68 GYMNOSPERMS 



erous. Material has been collected in the Carboniferous and Per- 

 mian of Europe, North America, and China; in the Permian of 

 Russia and Siberia; and in the Permo-Carboniferous of India, Aus- 

 tralia, South Africa, and South America. 



LIFE-HISTORY 



While the life-history has not been worked out as thoroughly as 

 that of the Cycadofilicales, the structure of the wood and leaves has 

 been studied in detail, and something is known of the reproduction. 



ScoTT^^^ treats the order, Cordaitales, under three families, the 

 Poroxylae, Pityeae, and the Cordaiteae, which, for the sake of the 

 usual family ending, might be called the Poroxylaceae, Pityaceae, 

 and the Cordaitaceae. The first family has only one genus, Poroxy- 

 lon; in the second, the principal genera are Pitys, Callixylon, and 

 Dadoxylon; in the third, Cordaites is the best-known genus, but 

 Mesoxylon, Parapitys, Mesopitys, and others have received atten- 

 tion. Some of the names suggest resemblances to members of the 

 second family. 



Krausel,^^' in Die naturlichen PJlanzenfamilien, arranges the 

 material, provisionally, under four families, based largely upon the 

 endarch or mesarch character of the primary bundles and their 

 distribution. 



THE SPOROPHYTE — VEGETATIVE 



The stem. — The stem, in most forms tall and slender, and branch- 

 ing only at the top, with dense clusters of leaves, suggests that the 

 plants grew in crowded stands, forming a deep shade. 



In the reconstruction of the Carboniferous swamp-forest in the 

 Field Museum of Natural History, at Chicago, a Cordaites with 

 large leaves was chosen to represent this important group (lig. 179). 

 The general appearance, as the spectator views the realistic scene, is 

 probably correct, but in another reconstruction the Dory-Cordaitcs 

 leaf is combined with the Eu-Cordaitcs fructification, as in the well- 

 known restoration of Grand d'Eury. 



In transverse section, the topography of the stem of some species 

 of Cordaites resembled that of a cycad, with large pith, scanty wood, 

 and large cortex, as in Cordaites {Mesoxylon) sutdiffii (llg. 180). In 

 Mesoxylon multirame the topography of the stem bears a striking 



