PLANTS OF THE INDIAN DESERT. 6? 



with green bundle-sheaths. Larger veins vertically transcurrent. 

 Clothing hairs two-armed. Glandular hairs absent. Fericycle formed 

 of isolated stone-cells and of very small stone-cell groups. Assimilatory 

 tissue in the axis formed of chlorenchyma. Wood composite. Pith 

 of thick- walled cells. 



Convolvulus microphyllus Sieb — Figs. 228, 229. Guard- 

 cells elevated. Front cavity placed in a depression formed by outer 

 thickened epidermal walls. Mesophyll isobilateral. Veins embedded 

 and provided with green bundle-sheaths. Internal glands and oxalate 

 of lime absent. Terminal cell of the clothing hairs seated obliquely 

 on the stalk cell. External glands spherical on the leaf and club- 

 shaped on the axis. Pericycle formed of thin long groups of stone- 

 cells. Aasimilatory tissue in the axis formed of palisade cells. Wood 

 composite and narrowed on two opposite sides. Pith of thin-walled 

 cells. 



Convolvulus glomeratUS Chois.— Fig. 230. Guard-cells ele- 

 vated. Front cavity on a level with the surface. Mesophyll of 

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

 abaxial side. Secretory cells with surrounding subsidiary cells present. 

 Oxalate of lime absent. Veins embedded and without bundle-sheaths. 

 Clothing hairs with terminal cell vertically placed on the stalk cell. 

 External glands club shaped. Assimilatory tissue in the axis paren- 

 chymatous. Pericycle of closely placed thin long groups of stone-cells. 

 Wood composite and narrowed on two opposite sides. Pith of thin- 

 walled cells. 



Ipomoea sindica Stapf.— Figs. 231, 232, 233, 234, 235. Guard- 

 cells elevated. Front cavity on a level with the surface. Mesophyll 

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

 the abaxial side. Internal glands absent in the leaf and found in the 

 axis in the form of secretory cells with tanniniferous contents. 

 Oxalate of lime absent. Terminal cell of clothing hairs superficially 

 knobbed and seated vertically on the stalk-cell which is placed on an 

 epidermal cell in the leaf and on a multicellular pedestal on the axis. 

 External glands horizontal. Assimilatory tissue in the axis par- 

 enchymatous. Wood composite and narrowed on two opposite sides. 

 Pericycle forming a composite ring of stone-cells. Pith of thin-walled 

 cells with granular contents. 



Structure of the Leaf: — The epidermis consists of tabular cells 

 with the outer walls thickened and convexly arched outwards ; 

 inner walls are also thickened. The lateral walls are thin and straight. 

 The cuticle is thin and striated. 



The stomata are developed equally on both the surfaces of 

 isobilateral leaves ; they are more numerous on the lower surface of 



