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. 
I. Cell cavity. 
2. Porous walls. 
3. Pitted end walls 
