PLATK XXV. 



A, I'INUS IIETEBOPHYLLA. Radial and taugential sections of a transverse resin duct; r. d., resin duct; . r., medul- 

 lary ray; tr,, tracheids of the medullary ray; p., parenchyma cells of the same; r. tr., common tracheids or 

 wood fibers. 



B-(T, PINUS GLADRA. H, tangential section of a transverse resin duct and parts of three fibers; l>. p., bordered pit; 

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

 while D is a " triple " ray. 



H, PlNL'S T/EDA. Tangential sections of medullary rays in spring and summer wood. 

 Original magnified 500 times, illustrations about a f. 

 162 



