PLATE 90
Ruellia Root (Ruellia ciliosa, Pursh.).
1. Epidermis with root hair. 2. Parenchyma cells with dark contents. 3. Sclerid. 4. Parenchyma without dark cell contents. 5. Endodermis. 6. Bast fibers and phloem. 7. Cambium. 8. Xylem. 10. Pith.
The stone cells are porous and striated, and the walls are thick and white.
Endodermis. The endodermal cells are tangentially elongated, and the walls are thin and white.
Pericycle. The cells forming the pericycle are the sieve cells, bast fibres, and phloem parenchyma.
The sieve cells are small, angled cells with thin, white walls.
The phloem parenchyma cells resemble the sieve cells, but they are larger.
The bast fibres occur singly or in groups of two or three. They are rounded in outline, and the walls are white, non-porous, and non-striated.
Xylem. The xylem is composed of vessels, wood parenchyma, and wood fibres.