Page:The Journal of Indian Botany.djvu/496

 and possess a few small vessels. The wood-ring in G, cretica is much narrowed on one side where there are a few small vessels.

These modifications in the structure of wood may be due to the influence of the direction of the prevailing wind in the first case, and to the inclined position of the axis in the second case. The reduction of wood, accompanied also by reduction of the sclerenchymatous pericycle in G. cretica,, takes place on those sides of the axis which are less affected by the prevailing wind and on the lower side of the inclined axis which is less exposed to the sun and wind and possess consequently less functional activity.

Vascular bundles in all members are bicollateral and there are two rings of soft-bast, one on the outer side and another on the inner side of the wood-ring.

The pith consists of thin-walled cells in all members except in B. latifolia where it consists of cells with thickened and lignified walls. The pith cells in I. sindica are mostly filled with granular contents.

General Revieiv. — The epidermal cells are not much thick-walled ; but have the outer and inner walls convexly arched outwards and inwards respectively. The guard-cells are elevated and are associated with subsidiary cells. The mesophyll is either isobilateral or is composed of palisade tissue on the upper side and of arm-palisade tissue on the lower. Internal glands, when present, consist of colourless secretory cells with surrounding subsidiary cells or of secretory cells with tanniniferous contents. Veins are embedded with the exception of some of the larger veins which are vertically transcurrent ; they may or may not be provided with bundle-sheaths. Oxalate of lime occurs in the form of clustered or solitary crystals, or it may not be found.

The clothing hairs are composed of a stalk-cell, seated upon a single epidermal cell or on a pedestal and of a terminal cell which may be simple and placed vertically or obliquely on the stalk-cell, or which may be two-armed. External glands are placed in epidermal depressions and are composed of a stalk-cell and of a head which may be club-shaped, spherical or horizontal. The head may be divided only by horizontal or vertical walls or by both.

The assimilatory tissue in the axis is composed of palisade cells or of chlorenchyma. The pericycle either forms a composite ring of stone-cells, or is formed either of large groups of stone-cells or of isolated stone-cells. Vascular bundles are bicollateral and the wood is composite. Interfascicular wood prosenchyma is not abundant and medullary rays are uniseriate. The wood as well as the pericycle undergo modifications due to differences in functional activity in dif-