PLATE XV. 



Fig. 65. Cross section of wood, No. 1, in fourth year, showing - wood 



fiber, medullary rays, and part of cross section of tracheal tube. (Heavy 

 wall.) X 275. 



Fig. 66. Cross section of wood, No. 2, in fourth year, x 275. 



Fig. 67. Cross section of wood, No. 3, in fourth year, x 275. 



Fig. 68. Cross section of wood, No. 4, in third year, x 275. 



