332 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



which indicates their relation to the evolution of higher types of 

 organization. The ray presents few features of value in the 

 transverse section, and these will be sufficiently dealt with in 

 the systematic portion^ to make further reference to them at this 

 time unnecessary. It only remains to point out that those rays 

 in the Abietineae which contain resin canals, and which present 

 an unusual width, possess no special diagnostic value in this 

 plane of section. 



Radial Section.— Viewed radially, the medullary ray is seen 



to be composed of a series of cells extended in a radial direction 

 and superimposed so as to form a muriform band from one to 

 many cells in height. In general terms, the higher the ray the 

 lower the component elements, from which it follows that in one- 

 celled rays the cells are usually highest ; but this feature is only 

 of general interest since it rarely has a bearing upon the chief 

 questions at issue. In some cases two structural types may be 



series, will appear in the Transactions of the ^ Ro^al' Society of Canada for 1^4- 



