Page:The Journal of Indian Botany.djvu/494

 bifacial leaves of C. glomeratus and /. sindica. Guard-cells are elevated in C. microphyllus (tig. 228), G. glomeratus and I- sindica (figs. 231, 232); they are placed in the plane of surrounding cells in other members. The guard-cells are accompanied by subsidiary cells except in C. cretica. The front cavity is on a level with the surface in C. glomeratus and I. sindica (fig. 233) ; in other members it is placed in a depression formed by thickened outer epidermal walls. The elevated position of the guard-cells may be due to the occurrence of a dense protective covering of clothing hairs.

The mesophyll is isobilateral (fig. 228) in all members except C. glomeratus and I. sindica (fig. 231), in which it consists of palisade tissue on the adaxial side and of arm-palisade tissue on the abaxial side.

Internal secretory organs occur in the form of secretory cells in the middle of the mesophyll of B. kitifolia and C. glomeratus and in cortex and pith of I. sindica (fig. 234 G). In B. latifolia and G. glomeratus they consist of colourless secretory cells with surrounding arm-palisade cells differentiated into subsidiary cells. Secretory cells in /. sindica are greatly horizontally elongated and hold tanniniferous contents.

Oxalate of lime occurs in the form of clustered crystals in the neighbourhood of veins and in the cortex and pith, and in the form of solitary crystals in the soft bast of B. latifolia. In other members oxalate of lime is not found.

The veins are embedded except some of the larger ones in B. latifolia which are vertically transcurrent above and below by collen. chyma. The veins in G. cretica, B. latifolia and G. microphallus (fig. 228) are provided with green bundle-sheaths. Vascular bundles of the veins are bicollateral.

Hairy covering consists of clothing and glandular hairs. Clothing hairs are composed of a terminal cell of variable shape and of a stalk-cell seated either upon a single epidermal cell, or on two epidermal cells formed by a vertical wall (fig. 231), or on a multicellular pedestal of epidermal cells (fig 235).

The terminal cell is simple and is seated straight upon the stalk-cell in C. glomeratus (fig. 230) or seated obliquely on the stalk-cell in C, microphyllus (fig. 228). In 1. sindica the stalk-cell of clothing hairs on the leaf is placed vertically on a single epidermal cell or on two epidermal cells formed by a vertical division wall (fig. 231) ; the stalk-cell on the axis is seated vertically on a multicellular pedestal of epidermal cells (fig. 235). The terminal cell bears minute solid knobs on the surface.

In G. cretica (figs. 224, 225) and B. latifolia (fig. 226), the terminal cell is two-armed ; arms are of uniequal length and are horizontally