PLATE 52 



A. Longitudinal section of the pith parenchyma of grindelia stem (Grin- 

 delia squarrosa, [Pursh] Dunal). 



1. Cell cavity. 



2. Cross-section of the porous end wall. 



3. Surface view of the porous side wall. 



B. Cross-section of the pith parenchyma of grindelia stem. 



1. Cell cavity. 



2. Porous walls. 



3. Pitted end walls 



