1902.] 



NATUEAL SCIENCES OF PHILADELPHIA, 



471 



delimitation of the annual rings of wood. An enumeration of the 

 tracheids in a single row from pith 1o cortex is here given, as an 

 expression of the relative size of each annual ring. The wood of 

 the stem from which the enumeration is made is one inch diameter. 



Table II. 



The tracheids of the first three years of growth are more rounded 



