PLATE XXV. 



Fig. 16. Portion of xylem with tracheal tubes, x 295. 



Fig. 17. Surface view of epidermis of stem, x 295. 



Fig. 18. Fitter tracheal tubes, x 335. 



Fig. 19. Medullary ray cells as seen in longitudinal section, x 630. 



Fig. 20. Epidermis of stem, x 315. 



Fig. 21. Pith cells, x 295. 



Fig. 22. Palisade cells as found in the pericycle of old stems, x 280. 



cork; B, parenchyma. 



Fig. 23. Stoma of stem, x 315. 



