PLATE XXVI. TANGENTIAL SECTIONS. 



A-C and F, PINUS HETEROPHYLLA. D, PINUS ECUINATA. E, PINUS GLABKA. 

 A--C, sections of medullary rays; tr., tracheids; p., parenchyma; C is a "double" ray. 



In D-F, histological details are omitted; they are camera drawings showing number and distribution of medullary 

 rays, and also the proportion of the tracheids to parenchyma in each ray, the former being indicated by dots; 

 r. d., transverse resin ducts; TO. r., medullary rays. 



Magnification of originals: .4-C, 4 ? Q ; D-F, 11 ?; of illustrations: A-C, *?; D-F, *,*. 

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