196 ANATOMY OF THE GYMNOSPERMS 



Pits on the lateral walls of the ray cells small, simple, elliptical. 

 Terminal walls of the ray cells more or less strongly pitted. 



1 6. Abies (p. 253). 



B. Resin passages and fusiform rays wholly wanting. 



I. Tracheids (radial or tangential) bearing thin spiral bands in 1-4 series. 



Ray cells (tangential) narrowly oblong. 



Tracheids (transverse) chiefly thick-walled and variable, the lumens usually 

 conspicuously rounded, the structure somewhat compact (except T. flori- 

 dana), the spirals rather close. 



6. Taxus (p. 212). 

 Ray cells (tangential) broad, oval, or oblong. 



Tracheids (transverse) large, chiefly squarish, and rather thin-walled, the 

 structure rather open throughout, the spirals rather open. 



5. Torreya (p. 210). 

 II. Tracheids (radial or tangential) wholly devoid of spirals. 



1. Wood nonresinous, commonly bearing idioblasts with sphere 



crystals; the tracheids of 2 kinds (transverse). 



4. Gingko (p. 209). 



2. Wood resinous, devoid of crystal-bearing idioblasts ; the tracheids 



(transverse) all of i kind. 



Resin cells (transverse) prominent and in more or less conspicuous, tangential 

 bands, sometimes of distant growth rings or again widely scattering. 

 Terminal walls of the ray cells entire, straight, more rarely curved. 



Pits on the lateral walls of the ray cells large, with a distinct border. 

 Resin cells distinctly zonate. 



Pits on the lateral walls of the ray cells round, the narrowly 

 oblong orifice distinctly diagonal, the border very prominent. 



10. Taxodium (p. 217). 

 Resin cells scattering. 



Pits on the lateral walls of the ray cells oval, the oblong or len- 

 ticular orifice usually parallel with the cell axis, the border 

 often narrow, sometimes obscure. 



13. Sequoia (p. 223). 

 Terminal walls of the ray cells sparingly pitted. 



Pits on the lateral walls of the ray cells wholly simple or with an incon- 

 spicuous border, chiefly small. 



Rays (tangential) broad, very sparingly resinous, often 2-seriate at 

 least in part. 



11. Libocedrus (p. 219). 



Pits on the lateral walls of the ray cells distinctly bordered. 



Rays (tangential) usually rather narrow, more or less strongly resin- 

 ous, i -seriate. 



15. Juniperus (p. 244). 



Terminal walls of the ray cells entire or locally thickened, usually much curved, 

 sometimes straight. 



