PART II SYSTEMATIC 



SYNOPSIS OF GENERA FOR THE CORDAITALES, 

 GINGKOALES, AND CONIFERALES 



A. Resin passages and fusiform rays present. 



I. Fusiform rays narrow, the terminals chiefly long and abruptly linear ; 

 the cells rather small and thick-walled. Resin passages with thick- 

 walled epithelium and chiefly without thyloses. 



Tracheids (radial) with spirals, at least in the spring wood. 



Resin cells scattering on the outer face of the summer wood. 



18. Pseudotsuga (p. 271). 

 Tracheids wholly without spirals. 



Pits on the tangential walls of the summer tracheids. 



Resin cells present but scattering on the outer face of the summer wood. 



19. Larix (p. 276). 

 Resin cells wholly wanting. 



20. Picea (p. 281). 



II. Fusiform rays (tangential) chiefly broad, the cells large, the resin 

 passages broad with thin-walled epithelium and strongly developed 

 thyloses. 



Tracheids wholly without spirals. 

 Resin cells wholly wanting. 



Pits on the tangential walls of the summer tracheids. 

 Ray tracheids not dentate. 



21. Pinus (Section I, p. 305). 



Pits on the tangential walls of the summer tracheids usually wanting. 

 Ray tracheids dentate. 



21. Pinus (Section II, p. 318). 



III. Fusiform rays (tangential) wholly wanting. Resin passages (trans- 

 verse) when present usually in compact rows on the outer face of 

 the summer wood of distant growth rings, imperfectly formed. 



Resin cells prominent. 



Pits on the lateral walls of the ray cells usually with a conspicuous border, 

 the orifice very large, oblong, the pits very prominent. 



13. Sequoia sempervirens (p. 224). 



Pits on the lateral walls of the ray cells very small, with a narrowly oblong 

 orifice. Terminal walls of the ray cells strongly pitted. 



17. Tsuga Mertensiana (p. 270). 



Resin cells remote and more or less obscure on the outer face of the summer wood 

 or wholly wanting. 



'95 



