PLATE XXIII.— RADIAL SECTIONS. 



A and B, PiNUS echinata. m. r., medullary rays; p., parenchyma of same; tr., tnmsvcrsi! tracliciils nt' rays; s. p., 



simple pits; b. p., bordered pits; c. tr., common tracbeids. 

 C, I'iNUS HETEKOPHYLLA. »M. «'., summerTCOod ; other letters as in .(. 

 Originals magnified "fO; illn.strations, ^j^. 

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