136 MORPHOLOGY OF SPERMATOPHYTBS 



in display to the Carboniferous, when they were astonishingly 

 abundant, the leaves often being packed together in masses on 

 every layer of the deposits. It seems clear that this was the pre- 

 vailing Gymnosperm forest type of the Paleozoic. They were 

 tall, rather slender trees, with shafts from 10 to 30 meters in 

 height, branching only above, and with a dense crown of 

 branches on which simple large leaves were produced in great 

 abundance (Fig. 94). The leaves were usually long, ribbonlike, 

 and parallel-veined, from 20 to 100 centimeters long and 15 to 

 20 centimeters broad. Scott 6 says that " the habit of the Cordai- 

 tales must have been different from that of any trees with which 

 we are now familiar. The species with comparatively short 

 leaves may be compared with such Coniferae as Dammara (the 

 Kauri Pine of New Zealand), or with some forms of Podo- 

 carpus, and these trees may best serve to give us some idea of 

 the extinct family. But the large-leaved species must have had 

 a habit very different from anything which we are accustomed 

 to associate with the Gymnosperms at the present day." 



The anatomical character of the stem is in general plan that 

 of the Conifers, but the very large pith, which appears in trans- 

 verse diaphragms, is more suggestive of the Cycads. As in Coni- 

 fers, the tracheary tissue begins with spiral vessels lying next 

 to the pith, and the secondary wood is composed exclusively 

 of tracheids with bordered pits which are usually in two or more 

 rows and are densely crowded, so that they have a hexagonal out- 

 line. As this secondary wood resembles very closely that of 

 Araucaria, it was named Araucarioxylon by Kraus. The cor- 

 tex contains strands of fibrous sclerenchyma, and isolated gum 

 receptacles. 



The leaves have conspicuous parallel veins, and in the major- 

 ity of forms are elongated and strap-shaped, having very much 

 the appearance of such monocotyledonous leaves as those of 

 Yucca or Dracaena. The venation is repeatedly dichotomous, 

 excepting in the narrowest leaves, which are almost grasslike. 

 Sometimes, however, the leaves are short and obovate, and are 

 said occasionally to branch dichotomously and even to become in- 

 cised. In such leaf forms and venation there are suggestions of 

 Ginkgo and of certain Ferns, while the ordinary elongated type, 

 with its parallel veins, suggests Tumboa. 



The anatomical character of the leaf is practically that of 



