174 THE ELEMENTS OF VEGETABLE HISTOLOGY 



less, thin-walled, rectangular cells, immediately beneath 

 the corky tissue. The walls of these cells are of cellu- 

 lose and may be readily distinguished from the su- 

 berized cork cells by micro-chemical tests. The phel- 



PLATE 59. Bark Structure (Powdered material). 



A. Chionanthus, root bark. 1. Bark parenchyma (longitudinal view), con- 

 taining starch, crystals and resin masses. 2. Bark parenchyma crossed by medul- 

 lary ray cells. 3. Cork tissue. 4. Bark parenchyma (transverse view). 5. Fibers. 

 6. Crystals. 7. Stone cells'. 8. Resin masses. 



loderm consists of one or more layers of rather thick- 

 walled cells located beneath the phellogen. These 

 cells are irregular in form and may be similar to col- 

 lenchyma in appearance. The phellogen always pro- 



