Page:The Journal of Indian Botany.djvu/330

 stals in the neighbourhood of the veins in T. triquetra, T. pentandra, 0. decumbens, M. nudicaulis and L. indicum. Besides clustered crystals near the veins, there are solitary ones in the spongy cells of M. nudi- caidis (fig. 151). Palisade cells on both sides, in M. hirta (fig. 150) and M. Gerviana (fig. 154), contain small bundles of needle-like crystals and solitary crystals respectively. Oxalate of lime is found in the form of bundles of acicular raphides in G. pharnaceoides.

The veins are embedded in all members ; they are provided with bundle-sheaths of green, thin-walled cells in T. pentandra and M. Cerviana. Sheath-cells are colourless in L. indicum. Veins in T. triquetra, are provided only on the lower side with arcs of green bundle-sheath cells, owing to the occurrence of the assimilatory tissue on the sides of the veins.

Hairy covering on the leaf and axis is found only in M. hirta and consists of stellate hairs with an uniseriate stalk and a star-shaped terminal cell (figs. 148, 149, 150). In L. indicum (fig. 157), there are papillae-like unicellular structures with walls thickened and superfi- cially rugose. They may have been developed from epidermal out- growths which were afterwards separated by transverse walls ; they may have a water-storing function. External glands are found only in L. indicum in the form of capitate glandular hairs (figs. 157, 159).

Structure of the Axis. — The epidermis consists of polygonal cells with outer walls thickened. Lateral walls are thin and undulated Inner walls are also thickened in T. triquetra, T. pentandra, 0. decumbens, M. hirta and G. phamaceoide. There are large bladder- like cells, attenuated at their apices into hair-like structures, inter- calated among-it epidermal cells of ordinary dimensions in T. triquetra (fig. 140) and in T. pentandra (fig. 143). These cells may have a water-storing function. The stomata are like those on the leaf.

The primary cortex is represented by a thin-walled parenchy- matous assimilatory tissue in 0. decumbens and in species of Mollugo. Collenchyma is developed in the angular portions of 0. decumbens. The primary cortex, in other members, is formed of colourless cortical parenchyma.

The pericycle is formed of a more or less composite ring of stone- cells in 0. decumbens (fig. 146), species of Moll tig o (figs. 149, 153, 155) and G. pharnaceoides. In species of Moll tig o the ring of stone tissue is very thick. The pericycle in L. indicum, consists of rhomboidal groups of stone-cells ; in other members it is not sclerenchymatous, which is compensated for perhaps by extensive interfascicular wood prosenchyma which is very little developed in species of Mollugo. It seems, therefore, that the development of sclerenchymatous pericycle is inversely proportional to that of interfascicular wood prosenchyma.