H. Doc. 181. 



Plate XXV. 



m*~n 



f-itij'. 



/•€»£•« 



...\r.d 



m.n 





B 



~P- 



C 



~-nd 



Tangential Sections of Pinus echinata, heterophylla, and glabra, showing Num3er and Distribution of 



Pith Rays and Proportion of Pith-ray Cells. 



A-C and F, Pinus heterophylla. 2), Pinus echinata. JS7, Pinus glabra. 



A~C, Sections of medullary rays; tr., traeheids; -p., parenchyma; C is a " double " n ray. 



In D-F histological details are omitted; they are camera drawings showing number and distribution of medullary rays, and also 



the proportion of the tracheitis to parenchyma in each ray, the former being: indicated by dots; r. d , transverse resin 



ducts; m. r., medullary rays. 

 Magnification of originals: A-C\ 5 ? Q ; D~F, *£; of illustrations: A-C, 3 p; D-F, -",?■ 



