STRUCTURE OF EXOGKNOFS STEM*. 



FIG 46. TRANSVERSE AND PERPENDICULAR SECTIONS OF & STEM FOUR YEARS OLD ; 

 the latter through the pith, a, pith and wood of the first year ; b, c, d, layers of wood 

 of the second, third, and fourth years ; e, the four thin layers of bark. 



lilillll 



FIG. 47 SECTIONS ar A STEM AS IT APPEARS IN MAY OR JUNE OF THB FIFTH YK 

 The white spaces show the swelling cambium. 



FIG. 48. SECTIONS OF A STEM AT THE END OF THE FIFTH YEAR. The envelopes and 

 layers of liber are too thin to be shown by the pencil. 



In this way we can account for the extraordinary number of 

 layers, in the Baobab trees of Senegal ; without having recourse 

 to the supposition, that they were above 5000 years old, as we 

 must otherwise regard them. 



1 30. Each layer of wood consists partly of vessels or ducts, 



