PLATK XXI\'.— RADIAL AND TANGENTIAL SKCTIONS. 



A uikI />', PiNUS T^DA. Radial sections; m. r., niediillary r:iy8; tr., tniclieids; j)., ]iareiicliyiiia of tlio rays; «. p., 



simpli' pit ; b. }>., bordered pit; c. //•., comimiM traclieids. 

 ('-/;, taiij;intial sections. 



r, I'lNis I'Al.usTnis. Left-hand part in sprin^wnod, right-liand portion in snninifrwond. 



D-£, I'lXUS ECHINATA. D, Section iu springwood ; «-c, medullary rays; a, a small ray comjiosicl of traclieids only; 

 c, a " triple" ray ; <f, bordered pit showing the membrane in place. 7^, Section in summerwood; a. bordired 

 pit, other letters as in .( and II. 

 Magnification of originals, ^''; of illustrations: A and Jt, -{"; C-E, ^'i'". 

 150 



