Page:The Journal of Indian Botany.djvu/133

 Glandular hairs in Abutilon fruticosum, Pavonia arabica and Hibiscus micranthus (fig. '57) are club-shaped and are composed of a basal stalk-cell and of a head divided by horizontal and vertical walls. Sida grewioides (fig. 54) possesses pitcher-shaped uniseriate glandular hairs. External glands in Gossypium herbaceum (fig. 59) are spherical and are composed of a basal stalk-cell and of a head irregularly divided. External glands are numerous on both the surfaces of the leaf and are placed in depressions of the epidermis in all members except Abutilon fruticosum. They are more numerous on the lower surface in Sida grewioides and on the upper surface in Gossypium herbaceum.

Structure of the Axis:—The epidermis consists of small tabular cells with outer walls thickened and papillose. The lateral walls are straight. The hairy covering is composed of tufted hairs as described already. Besides the tufted hairs there are thick-walled unicellular hairs, resembling the rays of the tufted hairs, in Pavonia arabica. External glands occur on young branches and have the same characters as of those on the leaf.

The primary cortex is characterised by subepidermal cork in Sida grewioides, Abutilon fruticosum (fig. 56) and Gossypium herbaceum (fig. 60). Collenchyma occurs in the cortex in all members; it may form long strands as in Pavonia arabica or a continuous ring as in other species. Assimilatory tissue consists of palisade cells in Hibiscus micranthus (fig. 54) ; in other species it is formed of chlorenchyma.

The pericycle is composed of closely placed rhomboidal groups of stone-cells; it is reduced on the lower side of the inclined branches of Hibiscus micranthus. There are numerous small groups of bast fibres in the soft bast of Sida grewioides and Pavonia arabica.

The wood forms a composite hollow cylinder in all members. The vessels are small and arranged in closely placed rows. The interfascicular wood prosenchyma is not very extensive. The medullary rays are uniseriate in Sida greioioides and Pavonia arabica; in others they are 1-3 seriate. In Abutilon fruticosum there occur vascular bundles in the pith close to the xylem cylinder. On a small portion of the axis in Pavonia arabica, Hibiscus micranthus and Gossypium herbaceum the wood is reduced; in this portion of the axis the wood is much narrowed and vessels are few and small. This may be accounted for by the inclined nature of the axis, the wood being reduced on the lower side.

The pith consists of thick-walled cells in Abutilon fruticosum; it is composed of thin-walled cells in others.

Internal glands occur in the cortex in the form of secretory