CHAPTER IX 

 CONIFEROPHYTES— CORDAITALES . 



The other great Hne of gymnosperms is the Coniferophytes, com- 

 prising four groups, the Cordaitales, Ginkgoales, Coniferales, and 

 Gnetales, whose relation to each other is obscure. 



As contrasted with the Cycadophytes, they are, prevaihngly, 

 much larger plants, with profusely branched stems and simple 

 leaves. A transverse section of the stem shows a large pith, rather 

 scanty zone of wood in some forms, and a fairly large cortex. But, 

 while these features recall the Cycadofilicales, there are, within the 

 order, forms with rather small pith, extensive zone of wood, and 

 small cortex, approaching the condition characteristic of the Co- 

 niferales. Like the Cycadofihcales, they are all phyllosiphonic. 



The living forms belong as dominantly to the temperate zone as 

 the Cycadales belong to tropical and subtropical regions. Many 

 flourish where the winter temperature becomes colder than 4o°F. 

 below zero. 



The geological history goes back as far as that of the Cycadophytes, 

 probably much farther back. A provisional diagram is shown in 

 fig. 2. In this diagram no attempt has been made to show the rela- 

 tion of the six families under which we shall treat the Coniferales; 

 and we have not tried to attach the Gnetales to anything. 



The four great groups of the Coniferophytes will be treated 

 separately. 



Grand d'Eury,"^ C. E. Bertrand,^^ and Renault-'^s y^^ej-g pio- 

 neers in the investigation of this order. Among later investigators 

 whose names have become prominent are Scott, Oliver, P. Ber- 

 trand, Gordon, and others. Excellent textbooks, which are con- 

 tributions to knowledge as well as presentations of known material, 

 have been written by Scott,s"-s-'4 Seward,^^^-^^^ Solms-Laubach,s" 

 and Potonie."*^^ 



The Cordaitales formed the world's first great forests. Many of 



i6s 



