Page:The Journal of Indian Botany.djvu/135

 Melhania magnifolia, Blatfc. and Hall.

Lower surface of the leaf with furrows not deep. Mesophyll formed of palisade tissue on the adaxial side and of an arm-palisade tissue on the abaxial side. Numerous cells with tanniniferous con- tents near the veins. Solitary crystals occurring below the upper epidermis and near the veins of the leaf. Clothing hairs tufted. Glandular hairs club-shaped. Pericycle formed of a single loose ring of stone-cells. Vessels small and few. Medullary rays uni- seriate. Mucilage canals in the pith few.

Structure of the Leaf : — Epidermal cells are tabular, with outer walls a little thickened and convexly arched outwards. Lateral walls are straight. The lower surface is characterised by furrows which are much deeper in ilf. Denhamii. Stomata are more numerous on the lower surface and occur in the furrows ; they are surrounded by ordinary epidermal cells. Guard-cells are elevated and the front cavity is on a level with the surface. The mesophyll in M. Denhamii is composed of a homogeneous palisade tissue ; in M. magnifolia there is a palisade tissue on the adaxial side and arm-palisade tissue on the abaxial side.

Internal glands are represented in the axis by cells with mucil- aginous membranes in the cortical parenchyma and by numerous mucilage canals of schizogenous origin in the pith. In the leaf of M. Denhamii upper epidermal cells and numerous polygonal cells near the veins hold tanniniferous contents. Oxalate of lime occur in M. Denhamii in the form of solitary crystals near the veins of the leaf and in the cortical parenchyma and pith of the axis. In M. magni- folia bundles of solitary crystals occur near the veins and in a layer of tabular cells below the upper epidermis.

The veins are enclosed in green bundle-sheaths and are vertically transcurrent above by colourless parenchyma. The veins of the mid- rib are vertically transcurrent above by clourless thick- walled paren- chyma and below by collenchyma.

Hairy covering on the leaf and axis consists of densely placed tufted hairs which are more numerous on the lower surface. The rays are unicellular and thick-walled and are sunk directly in the epider- mis, so that the hairs seem to be formed by a group of epidermal cells (fig. 61). The rays on the lower surface of the mid-rib and on the axis are placed on a short multicellular stalk (fig. 62). The glandular hairs on the leaf and axis are club-shaped and are composed of a stalk- cell and a head divided by horizontal and vertical walls (fig. 62). The external glands are more on the upper surface and protect the palisade tissue against the strong light and glare by means of their secretions. 1480—14