SYNOPSIS OF GENERA 197 



Resin cells (transverse) rarely in bands, chiefly widely scattering, some- 

 times \vanting. 



Ray cells (tangential) narrowly oblong. 



12. Thuya (p. 220). 



Ray cells (tangential) rather broad, the cells round, oval or trans- 

 versely oval, rarely oblong. 



Summer wood usually thin and of open structure. 



Pits on the tangential walls of the summer tracheids usually 

 large and open, prominent. 



Rays (tangential) not very numerous. 



14. Cupressus (p. 228). 

 Rays (tangential) very numerous. 



9. Podocarpus (p. 216). 



Pits on the tangential walls of the summer tracheids very 

 flat and not very prominent. 



7. Thujopsis (p. 215). 



Summer wood dense, the spring wood open, thin-walled. 



8. Cryptomeria (p. 216). 

 Terminal walls of the ray cells thick, more or less coarsely pitted. 



Resin cells (transverse) not very prominent, remote, and more or less 

 obscure on the outer face of the summer wood, sometimes wholly 

 wanting (Abies). 



Rays (radial) without tracheids (rarely present in A. balsamea). 



16. Abies (p. 253). 



Resin cells (transverse) rather prominent, more or less numerous on the 

 outer face of the summer wood, rarely zonate. 

 Rays (radial) with conspicuous tracheids. 



17. Tsuga (p. 265). 



Resin cells (transverse) entirely wanting, being sometimes replaced by resinous 

 tracheids which are chiefly located along the medullary rays, or sometimes 

 scattering. 



Bordered pits multiseriate, hexagonal. 



Resin when present contained in tracheids (transverse) and forming plates 

 (radial) simulating Sanio's bands, or opposite rays (tangential). 

 Growth rings not determinable. 



Tracheids (transverse) chiefly equal and in very regular radial rows. 



1. Cordaites (p. 198). 



Tracheids (transverse) very unequal and in irregular, radial rows. 



3. Araucaria (p. 203). 

 Growth rings obvious, but poorly defined. 



2. Dammara (p. 203). 

 Bordered pits in i row. 



Resin when present contained in tracheids (transverse) and forming plates 

 (radial) simulating Sanio's bands, or opposite rays (tangential). 

 Growth rings not very well developed. 



3. Araucaria Bidwillii (p. 205). 

 Resin when present massive (radial), not in plates. 



Growth rings very prominent and well defined. 



16. Abies (p. 253). 



