254 



ANATOMY OF THE GYMNOSPERMS 



SYNOPSIS OF SPECIES 



i. Resin passages present but imperfectly developed 1 



Ray cells (tangential) all broad, oval, or round. 



Pits on the lateral walls of the ray cells 1-3, rarely 4, per tracheid. 

 Tracheids in regular rows. 



Resin cells on the outer face of the summer wood. 



10. A. concolor. 



Resin cells wanting. 



8. A. bracteata. 



Pits on the lateral walls of the ray cells chiefly 2, rarely 3-4, per tracheid. 

 Tracheids in regular rows. 



Resin cells wanting. 



9. A. nobilis. 



Ray cells uniformly narrow, oblong. 



Pits on the lateral walls of the ray cells obscurely bordered, greatly 

 reduced or wanting in the summer wood, 1-4, or in the marginal 

 cells 6, per tracheid. 



Resin cells wanting. 



1 1. A. firma. 



2. Resin passages wholly wanting 



Ray tracheids present, few. 



Resin cells (transverse) wanting. 



Ray cells (tangential) uniformly narrow, oblong. 



Pits on the lateral walls of the ray cells i -4, rarely 8, per tracheid. 



4. * A. balsamea. 

 Ray tracheids wholly wanting. 

 Resin cells wanting. 



Ray cells (tangential) uniformly narrow. 



Pits on the lateral walls of the ray cells 1-4, rarely 8, per tracheid. 



4. * A. balsamea. 



Pits on the lateral walls of the ray cells obscurely bor- 

 dered, greatly reduced or wanting in the summer wood, 

 1-4, or in the marginal cells 6, per tracheid. 



1 1 . A. firma. 



Pits on the lateral walls of the ray cells more or less obvi- 

 ously bordered, especially in the summer wood, chiefly 2 per 



tracheid. 



i. A. Fraseri. 



Ray cells (tangential) variable, from round or oval to narrowly 

 oblong. 



1 Species included in this section should also be looked for under the second 

 section with the same differentiation. 



