Wood Parenchyma. The wood parenchyma cells are small and angled.
Medullary Rays. The medullary ray cells are tangentially elongated, but in structure resemble the wood parenchyma cells.
Pith Parenchyma. The pith parenchyma cells are rounded in outline and contain small, simple, rounded starch grains.
CROSS-SECTION RUELLIA RHIZOME
The cross-section of ruellia rhizome (Plate 92) differs from the structure of spigelia rhizome. It is as follows:
Epidermis. The epidermal cells vary in shape from nearly square to oblong, and they are filled with dark-brown cell contents.
Cortex. The cortex contains parenchyma and stone cells.
The outer layer of the cortical parenchyma cells are variable in size and many of the cells contain deposits of calcium carbonate and dark cell contents; the inner parenchyma cells are larger and they are free of the dark-brown cell contents, but many of the cells contain deposits of calcium carbonate.
Stone cells with thick, white, porous, and striated walls occur in among the cortical parenchyma cells.
Phloem. The phloem contains sieve cells, phloem, parenchyma, and bast fibres.