THE GYMNOSPERMS 389 



represent a whorl. The leaves are hard and firm, have a thick 

 rather resinous cuticle, and a thick epidermis. Underneath the 

 epidermis are a few layers of stony (sclerenchyma) cells inside 

 of which is the thin-walled chlorophyll-bearing parenchyma with 

 fluted cell walls. There are one or two vascular ducts in the leaf 

 according to the species, besides the resin ducts. This structure 

 of the leaves, together with their small and compact size, fits them 

 to withstand the drying effect of cold winters, the heat of the sun 

 and severe droughts in summer. Some of the conifers are de- 

 ciduous, as the bald cypress, larch, etc. 



542. The structure of the stem and its development is much as 

 described for woody stems (paragraphs 102-106) but there are no 



Fig. 357- 

 Staminate cones of American yew (Taxus canadensis). 



trachea in the vascular system, these being represented by trache- 

 ides similar to the trachea but their cross walls not being per- 

 forated. The most characteristic feature of the wood is the 



