PLANTS OF THE INDIAN DESEET. 197 



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.) 



