Bulletin No. 13, Division of Forestry. 



Plate XXVI. 



D 



' m.r: 



r.d.-% 



r.d 



m.rr 



m.r. 



A 



B 



tP- 



-r.d 



Tangential Sections of Pinus echinata, heterophylla, and glabra, showing Number and Distribution of 



Pith Rays and Proportion of Pith-ray Cells. 



