266 ANATOMY OF THE GYMNOSPERMS 



Resin passages not present. 



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



Pits on the lateral walls of the ray cells 2-4, or in the sum- 

 mer wood 1-2, per tracheid ; the resin cells prominent, 



resinous. 



1. T. canadensis. 



Pits on the lateral walls of the ray cells 1-2, rarely 3, per 

 tracheid. 



Spring tracheids very large and uniform, conspicuously 

 4-sided, the walls thin. 



5. T. Mertensiana. 



Pits on the lateral walls of the ray cells very variable, at 

 first 5, soon uniformly 2, and finally I, per tracheid. 

 Spring tracheids squarish-hexagonal. 



2. T. Sieboldii. 



Resin cells on the outer face of the summer wood and also often 

 zonate in the spring or summer wood. 

 Resinous tracheids wanting. 



Pits on the lateral walls of the ray cells 2-6, finally i, 

 per tracheid. 



3. T. caroliniana. 



Resinous tracheids in groups or radial series in contact with 

 the rays. 



Pits on the lateral walls of the ray cells 1-4, chiefly 2, 

 and finally i, per tracheid, the orifice finally becom- 

 ing a prolonged slit. 



4. T. Pattoniana. 



1. T. canadensis, Carr. 

 Hemlock 



Transverse. Growth rings thin, variable. The thin and dense summer 

 wood prominent, equal to about one fourth to one half the spring 

 wood, from which the transition is abrupt. Spring wood very open, 

 the large and very thin-walled tracheids conspicuously squarish, often 

 elongated radially, very uniform and in regular rows. Resin cells 

 prominent, resinous, not very numerous. Medullary rays very promi- 

 nent, somewhat resinous, i cell wide, distant 2-10 rows of tracheids. 



Radial. Rays uniformly somewhat resinous throughout, the tracheids 

 often interspersed. Ray cells somewhat contracted at the ends, equal 

 to 3-5 spring tracheids ; the upper and lower walls medium, unequal, 

 very irregularly and often imperfectly, sometimes very sparingly, 

 pitted ; the terminal walls not very strongly pitted except in the 

 summer wood ; the lateral walls with small, oval pits, at first with 

 a very narrow border, which becomes more pronounced toward the 



