are thin and straight. The stomata occur on both the surfaces and are accompanied by subsidiary cells in B marrubifolia and by 4 or 5 ordinary epidermal cells in C. Phlomidis. The guard-cells are a little elevated and the front cavity is placed in depressions formed by thickened outer epidermal cells.
The mesophyll is composed of palisade tissue on the upper side and of arm-palisade tissue on the lower. Internal secretory organs and oxalate of lime are found neither in the leaf nor in the axis. The veins are embedded and are not provided with bundle-sheaths.
The hairy covering on the leaf and axis consists of clothing and glandular hairs. Clothing hairs occur in the form of unicellular or bluntly pointed uniseriate trichomes with muriculate walls. The clothing hairs are more numerous on the lower surface. The glandular hairs are placed in epidermal depressions. They are composed in C. Phlomidis of a stalk-cell and of a broadly disc-shaped head divided by many vertical walls (fig. 264). In B. marrubifoli (fig. 262), they consist of a short uniseriate stalk and of a disc-shaped head divided by an oblique wall.
Structure of the Axis.—The epidermal cells are tabular, with outer walls thickened and muriculate in B. marrubi/olia, and thin and convexly arched outwards in C. Phlomidis. The lateral walls are thin and straight. The primary cortex is composed on its outer side of collenchyma and on its inner side of cortical parenchyma. Cork is developed below the collenchyma in C. Phlomidis. Cortical parenchyma is of uniform breadth in G. Phlomidis and is more extensive in the plane exposed to the wind in B. marrubifolia.
The pericycle consists of a more or less composite ring of stone-cells in G. Phlomidis and of groups of stone-cells in B. marrubifolia. The stone-cell tissue is more extensive in the plane exposed to the wind in B. marrubifolia. The wood forms a composite hollow cylinder. The vessels are large and are uniformly distributed in incomplete rows in the extensive interfascicular wood prosenchyma. Medullary rays are 1-2 seriate and are numerous.
The pith consists of thin-walled cells.
LABIATAE.
Salvia aegyptiaca L—Figs. 265, 266, 267. Upper epidermal cells larger. Epidermal cells tabular with outer walls very greatly thickened. Stomata on both the surfaces and accompanied by subsidiary cells. Mesophyll formed of palisade tissue on the upper and of arm-palisade tissue on the lower. Internal glands and oxalate of
