Page:The Journal of Indian Botany.djvu/227

 parenchyma with numerous water-storing tracheicls. Pericycle formed of small groups of stone-cells. Vessels small and few. Interfascicular wood prosenchyma extensive. Medullary rays 1-2 seriate Xylem bundles occurring in the soft bast. Pith characterised by sieve-sclereids.

Structure of the Leaf.—The epidermal cells are tabular with outer and inner walls convexly arched outwards and inwards respectively. The outer walls are thickened. The cuticle is striated. The lateral walls are thin and straight. The stomata are depressed and are more numerous on the lower surface and are surrounded by ordinary epidermal cells. Guard-cells are situated in a plane a little below that of the surrounding cells (figs. 82, 84).

The mesophyll is composed of palisade tissue on the upper side and of spongy on the lower. Internal glands do not occur in the leaf and axis. Oxalate of lime occurs in the leaf in the form of solitary crystals and clustered crystals near the veins of the leaf and in the cortical parenchyma of the axis. The veins are embedded and are provided with green bundle- sheaths; they are protected on the lower side by sclerenchyma. There are numerous groups of water-storing tracheids with pitted markings, occurring at intervals between the veins.

The hairy covering on the leaf and axis consists of thick-walled unicellular straight or bent trichomes (figs. 82, 84.) External glands do not occur on the leaf and axis.

Structure of the Axis.— Epidermis 'consists of small vertically tabular cells with outer walls greatly thickened and convexly arched outwards. Cuticle is striated. The cortex is composed of arm-palisade tissue on its outer side and of colourless cortical parenchyma on the inner. The cortical parenchyma is distinguished by the presence of sclereids with concentric stratification and radial lamellae.

The pericycle is composed of small groups of stone-cells. The wood forms a composite hollow cylinder. The vessels are small and are arranged in incomplete rows. The interfascicular wood prosenchyma is extensive and is composed of thick-walled cells with small lumina. The medullary rays are 1-2 seriate. A few xylem bundles occur in the soft bast (fig. 83 ) and form an anomolous structure in the axis.

The pith is characterised by sieve sclereids (fig. 83) and is composed of thick-walled cells.

Commiphora Mukul Engl— Plate XI, Fig. 85. Epidermal cells of the l«aves with innerwalls gelatinised. Stomata present on