94 



ANCIENT PLANTS 



Araucarias than the other groups of Gymnosperms in 

 their leaf characters. 



The internal anatomy is often well preserved, and 



Si fa- 



Fig. 62A. Microscopic Section of Part of a Leaf of Cordaites 



v, Vascular bundle ; w, wood of bundle ; sh, its sheath ; s l , large sclerenchynia mass 

 alternating with bundles ; S 2 and S 3 , sclerenchyma caps of bundle ; P, soft tissue of leaf. 



there is a number of species of leaves whose anatomy is 

 known. As will be expected from the parallel veins, 

 in each section there are many vascular bundles run- 

 ning equidistantly through the tissue. 

 Fig. 62A shows the microscopic details 

 from a well-preserved leaf. In all the 

 species patches of sclerenchynia were 

 developed, and everything indicates 

 that they were tough and well pro- 

 tected against loss of water, even to a 

 greater extent than are most of the 



Ing. 628. Much-mag- *> . 



wood Elements leaves of living Gymnosperms. 



from Cordaites Stem seen J n ^Q Stems the pith Was much 



in longitudinal section, i i -i i /~* 



the type known as Arau- larger than that in living Gymnosperms 

 Note the (where the wood is generally very 



solid )' and k s ho r llow in older ste T' 



in several rows CXCCpt for dlSCS of tlSSUC aCFOSS the 



cavity. The internal cast from these 



.stems has been described before, and is seen in fig. 63. 



The wood was formed in closely packed radiating 



