PLATE XXVI.— TANGENTIAL SECTIONS. 



J-f'an<l F, PiNUS heteropiiylla. D, Pinus echinat.\. E, Pinu.s glabra. 

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



In /'-/■', hi.stological details are omitted; tbey are camera drawings showing number and distribution of medullary 

 rays, and also the proportion of the tracheids to pareu<:hyma in each ray, the former being indicated by dots; 

 r. il., transverse resin ducts; m.. »-., medullary rays. 

 Magnilicatiou of originals: A-C, ^'i"^; D-F, V; of illustrations: A-G, ^»-; D-F, \^. 



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