94 



ANCIENT PLANTS 



Araucarias than the other groups of Gymnosperms in 

 their leaf characters. 



The internal anatomy is often well preserved, and 



Fig. 62 A. 



-Microscopic Section of Part of a Leaf of Cordailes 



V, Vascular bundle ; w, wood of bundle ; sh, its sheath ; s', large sclerenchyma mass 

 alternating with bundles ; s'' and s^, 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 sclerenchyma 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 

 leaves of living Gymnosperms. 



In the stems the pith was much 

 larger than that in living Gymnosperms 

 (where the wood is generally very 

 solid), and it was hollow in older stems, 

 except for discs of tissue across 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 



Fig. 62B. — Much-mag- 

 nified Wood Elements 

 from Cordaites Stem seen 

 in longitudinal section, 

 the type known as Arau- 

 carioxylon. Note the 

 hexagonal outlines of the 

 bordered pits, which lie 

 in several rows 



