PLANTS OF THE INDIAN DESEBT. 105 



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 



