70 THE JOUKNAL OP INDIAN BOTANY. 



General Review: — Outer walls of the epidermal cells are thickened. 

 Guard-cells are accompanied by ordinary 4-6 epidermal cells and are 

 usually elevated above the plane of the surrounding cells. The mesophyll 

 is either composed wholly of palisade tissue or is isobilateral, or is 

 composed of palisade tissue on the adaxial side and of arm-palisade 

 tissue or spongy tissue on the abaxial side. Internal secretory cells 

 with tanniniferous contents are usually present in the leaf. The veins 

 are embedded and are in some species provided with bundle-sheaths. 

 Water-storing tracheids occur in the leaf and axis in some species. 

 Mutlicellular capitate glandular hairs are of common occurrence. 

 Peltate clothing hairs are present in Caclaba inclica. Primary cortex 

 is characterised by an assimilatory tissue composed either of chloren- 

 chyma or of palisade tissue. The pericycle is composed of groups of 

 stone-cells. The structure of the wood is composite. The soft bast 

 forms a continuous ring or occurs in groups. The pith is composed 

 either of thin-walled or of thick-walled cells. 



VIOLAGEAE. 



Viola Stocksii Boiss. — Epidermal cells of the leaf and axis 

 with inner walls gelatinised and with outer walls thickened and 

 muriculate. Palisade-like elongation of the epidermal cells character- 

 istic of the axis. Stomata present on both the surfaces. Guard-cells 

 elevated above the plane of the surrounding cells. Mesophyll formed 

 of palisade tissue on the adaxial side and of arm-palisade tissue on the 

 abaxial side. Internal secretory organs absent. Oxalate of lime in 

 the form of large clustered crystals in the leaf. Veins embedded and 

 not provided with bundle-sheaths. Hairy covering absent. Scleren- 

 chymatous pericycle absent. Wood composite. Vessels small and 

 arranged in numerous complete rows. Medullary rays uniseriate 

 Collenchyma occurring at the inner margin of the wood. Pith 

 composed of thin-walled cells. 



Structure of the Leaf : — The epidermis is composed of tabular 

 cells, with outer walls thickened, muriculate and convexly arched 

 outwards, and with inner walls gelatinised. Lateral walls are wavy. 

 The marginal epidermal cells have outer as well as inner^walls thick- 

 ened. The gelatinised inner walls of the epidermis can absorb and 

 retain water. The epidermis thus forms a kind of water-storing 

 tissue. Stomata occur on both the surfaces. Guard-cells are elevated 

 and are accompanied by subsidiary cells. The front cavity is on a 

 level with the surface. The mesophyll is composed of palisade tissue 

 on the adaxial side and of arm-palisade tissue on the abaxial side. 

 Internal secretory organs do not occur either in the leaf or axis. 



