The sieve cells have thin, white, angled walls.
The phloem parenchyma cells are frequently tangentially elongated, otherwise they resemble the sieve cells.
The bast fibres occur alone or in groups. The walls are thick, white and porous.
PLATE 96
Cross-Section of Stem of Ruellia ciliosa, Pursh.
1. Epidermis. 2. Collenchyma. 3. Parenchyma. 4. Sclerids. 5. Bast fibres. 6. Phloem. 7. Cambium cells. 8. Xylem. 10. Pith parenchyma.
Cambium. The cambium cells are rectangular in shape and the walls are thin.
Xylem. The xylem contains vessels, wood parenchyma, and medullary rays.
The vessels are large; the walls are thick, white, and angled.
The wood parenchyma cells are variable in size and shape and the walls are angled.