The mesophyll differs in structure in the two species. In M. pterygosperma (fig. 9G) it is composed of palisade tissue on the adaxial side and of spongy tissue on the abaxial side. In M. concanensis (fig. 98) the palisade tissue occurs on the upper side and is composed of rows of palisade cells separated by greatly elongated myrosin cells ; a single layer of arm-palisade cells occurs below the lower epidermis.
Internal secretory organs are abundantly developed, in the mesophyll of M. concanensis (fig. 98G.) They are partly composed of greatly elongated tabular cells between the rows of palisade cells and partly of horizontally elongated polygonal cells forming a more or less continuous layer on the inner side of the arm-palisade tissue. Secretory cells in M. pterygosperma (fig. 96G) are abundant in the palisade tissue and are repersented by palisade-like cells. Internal secretory cells hold yellowish brown contents and seem to be of the nature of myrosin cells.
Oxalate of lime occurs in the form of numerous clustered crystals near the veins and below the lower epidermis of M. concanensis. It is not found in M. pterygosperma.
Veins are embedded in both the 'species. They are enclosed in green bundle-sheaths in M. pterygosperma ; they are strengthened by arcs of stone-cells on their lower side in M. concanensis.
PAPILLIONACEAE
Heylandia latebrosa DC— Fig. 99. Epidermal cells poly- gonal. Large water-storing cells intercalated amongst ordinary epi- dermal cells. Mesophyll bifacial. Veins vertically transcurrent by sclerenchyma. Tannin sacs absent. Clothing hairs in the form of uniseriate trichomes with muriculate walls. External glands absent. Assimilatory tissue in the axis chlorenchymatous. Pericycle formed of bast fibres. Medullary rays uniseriate. Pith formed of thin- walled cells.
Crotalaria Burhia Ham.— Figs. 100, 101. Epidermal cells polygonal with lateral walls undulated. Large water-storing cells intercalated amongst ordinary epidermal cells. Mesophyll isobila- teral. Veins embedded and enclosed in bundlesheaths. Tannin sacs found near the veins. Clothing hairs in the form of uniseriate tricho- mes with muriculate walls. External glands absent. Assimilatory tissue in the axis formed of palisade cells. Pericycle formed of stone-cells. Medullary rays uniseriate. Pith formed of thin-walled cells. Cortical vascular bundles present.
(To be continued.)
