CHAPTER II 



CYCADOPHYTES— CYCADOFILICALES 



The two great groups, Cycadophytes and Coniferophytes, are very 

 distinct as far back as any historical evidence has been obtained. 

 The most striking differences are shown in fig. 3. 



The Cycadophytes are comparatively small, with unbranched 

 stems and pinnate leaves; while the Coniferophytes are large, pro- 

 fusely branched, and have simple leaves. A glance at sections of the 

 stems shows that the Cycadophytes have a large pith, scanty wood, 

 and thick cortex; while the Coniferophytes have a small pith, abun- 

 dant wood, and scanty cortex. The entire phylum is phyllosiphonic. 



The Cycadophytes include three orders, the Cycadofilicales, the 

 Bennettitalcs, and the Cycadales, of which only the Cycadales have 

 living representatives, the Cycadofilicales having become extinct in 

 the Triassic, and the Bennettitalcs in the lower Cretaceous. 



In the Cycadofilicales, the sporangia are borne on leaves, more or 

 less modified, but never grouped into a cone. 



In the Bennettitalcs, the female sporophylls have lost all resem- 

 blance to leaves and are grouped into a cone. The male sporophylls 

 are leaflike, forming a loose crown ; they are never grouped into a cone. 



In the Cycadales, both male and female sporophylls are grouped 

 into cones, except the female sporophylls of Cycas, which are in a 

 loose crown, like the male sporophylls of the Bennettitalcs. 



Throughout the Cycadophytes, the sporophylls are in simple stro- 

 bili or cones. 



In the Coniferophytes, most of the male sporophylls form simple 

 cones; but the female cones are compound, the sporophylls being 

 borne on shoots coming from the axils of bracts. The shoots may be 

 so reduced that their presence may seem theoretical rather than 

 actual. While these statements are general in their application, the 

 male and female cones of Dioon, and the male cone of Finns may be 

 taken as illustrations of typical simple strobili. The female cone of 

 Pinus is a typical compound strobilus. 



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