A. Cross-section of calamus rhizome (Acorus calamus, L.). 1, Intercellular space; 2, Parenchyma cells; 3, Secretion cavity. B. Cross-section of white pine bark (Pinus strobus, L.). 1, Parenchyma; 2, Secretion cavity; 3, Secretion cells.
PLATE 63
A. Cross-section of a portion of canella alba bark (Canella alba, Murr.).
1. Excretion cavity.
B. Cross-section of a portion of klip buchu leaf.
1. Epidermal cells.
2. Secretion cavity.
3. Secretion cells.
PLATE 64
A. Cross-section of bitter orange peel (Citrus aurantium, amara, L.). 1, Internal secretion cavity formed by the dissolution of the walls of the central secreting cells; 2, Secretion cells. B. Cross-section of white pine leaf (Pinus strobus, L.). 1, Epidermal and hypodermal cells; 2, Parenchyma cells with protruding inner walls; 3, Endodermis; 4, Secretion cavity; 5, Secretion cells.
In calamus (Plate 62, Fig. A) the cavity is larger than the surrounding cells; it is rounded in outline, and it contains oleoresin. These cavities are in contact with the ordinary parenchyma cells, from which they are easily distinguished by their larger size and rounded form.
The unicellular oil cavity of canella alba (Plate 63, Fig. A) is rounded or oval in cross-section and is many times larger than the surrounding cells. The wall, which is very thick, is of a yellowish color.
Secretion cavities vary greatly in form, according to the part of the plant in which they are found. In flower petals and leaves they are spherical; in barks they are usually elliptical; in umbelliferous fruits they are elongated and tube-like.