PLATE XXV. 



A, Pixus HETEROPHYLLA. Radial and tangential sections of a transverse resin duet; r. d., resin duct; m. r.. medul- 

 lary ray; ir., tracheids of tlie medullary ray; p., parenchyma cells of the same; e. Ii\, comuion tracheids or 

 wood fibers. 

 I1~G, PiNUS r.LABR.\. B, tangential section of a transverse resin duct and parts of three libers; h. p., bordered pit; 

 other letters as above; C-G, tangential sections of medullary rays, of which K is made up of traiheids only, 

 while D is a "triple" ray. 

 IT, PiNUS T.EDA. Tangential sections of medullary rays in spring and summer wood. 

 Original magniKed 500 times, illustrations about •'y". 

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