220 



MORPHOLOGY 



Taxodineae (8 genera and about 15 species), including the characteris- 

 tic American genera Sequoia (redwood) and Taxodium (bald cypress). 



FIG. 486. Transverse section of a pine needle, showing the epidermis (in which are 

 deeply sunken stomata) underlaid by several layers of heavy-walled cells (sclerenchyma), 

 the mesophyll with characteristic infolded walls and containing resin ducts, the distinct 

 bundle sheath (endodermis) surrounding the vascular region (stele), and the two parallel 

 vascular bundles (xylem directed towards the flat face of the leaf). 



Cupressineae (9 genera and about 80 species), including the cypress, 

 arbor vitae (false cedar), and junipers, the large genus being Juniperus, 



with about 30 species. This tribe is 

 peculiar among Coniferales in its opposite 

 (cyclic) leaves. 



Araucarineae (2 genera and about 20 

 species), known as araucarians or arau- 

 carian pines, and characteristic of the 

 southern hemisphere. 



Sporophyte. The general habit of the 

 sporophyte body is sufficiently indicated 

 by the familiar forms mentioned above 

 (also see fig. 955). The vascular cylinder, 

 FIGS. 487, 488. Staminate with its endarch bundles, its thick cylinder 

 cone .(487) and microsporophyiis of secO ndary wood composed of radially 



U88) of pine (the latter in two 



,iews). showing the two abaxial arranged tracheids with bordered pits, is 



sporangia and the sterile tip. well known (fig. 485). So far as known, 



