88 



ANCIENT PLANTS 



do not know when the Gymnosperms began; the well- 

 developed and ancient group of Cordaite^ was flourish- 

 ing before the Carboniferous period, and must therefore 

 date back to the rocks of which we have no reliable 

 information from this point of view, and the origin of 

 the Gymnosperms must lie in the pre -Carboniferous 

 period. 



The group of Gymnosperms includes a number of 

 genera of different types, most of which may be arranged 

 under seven principal families. In a sketch of this nature 

 it is, of course, quite impossible to deal with all the less- 

 important families and genera. Those that will be 

 considered here are the following: — 



Coniferales 



(see p. 90). 



Cordaitales 



(see p. 92). ' 



Ginkffoales f ^ . , 



{Genera both living and fossil. 

 Fossil forms undoubted so 

 far back as the Jurassic, 

 and presumably further. 

 Genera both living and fossil. 

 Fossils recognized as far back 



as the Lower Cretaceous. 

 Genera both living and fossil. 

 Fossils recognized as far back 



as the Jurassic. 

 Genera living and fossil. 

 '. Fossils recognized as far back 

 \ as the Cretaceous. 



1 Fossil only. 

 Characteristic of Devonian, 

 Carboniferous, and Per- 

 mian periods. 

 i Fossil only. 

 Poroxylon 4 Characteristic of the Carboni- 



\ ferous and Permian, 

 f Fossil and living, dating 

 Ginkgo -! back, apparently with little 



\ change, to PalEeozoic times. 



Araucarem, e.g. Monkey-puzzle 



Abietinece, e.g. Pine and Larch 



Cupressece, e.g. Juniper, Cypress 



Taxece, e.g. Yew 



Cordaitea, e.g. 



Poroxylea, e.g. 



We must pay the most attention to the two last 

 groups, as they are so important as fossils, and the 

 Cordaitece were a very numerous family in Coal Measure 

 times. They had their period of principal development 

 so long ago that it is probable that no direct descendants 

 remain to the present time, though some botanists con- 

 sider that the Taxecz are allied to them. 



Of the groups still living it is difficult, almost impos- 



