PLANTS OF THE INDIAN DESEBT. 103 



Glandular hairs in Abutilon fruticosum, Pavonia arabica and 

 Hibiscus micranthus (fig. '57) are club-shaped and are composed of a 

 basal stalk-cell and of a head divided by horizontal and vertical walls. 

 Sida greioioides (fig. 54) possesses pitcher-shaped uniseriate glandular 

 hairs. External glands in Gossypium herbaceum (fig. 59) are spherical 

 and are composed of a basal stalk-cell and of a head irregularly 

 divided. External glands are numerous on both the surfaces of the 

 leaf and are placed in depressions of the epidermis in all members 

 except Abutilon fruticosum. They are more numerous on the lower 

 surface in Sida grewioides and on the upper surface in Gossypium 

 herbaceum. 



Structure of the Axis : — The epidermis consists of small tabular 

 cells with outer walls thickened and papillose. The lateral walls are 

 straight. The hairy covering is composed of tufted hairs as described 

 already. Besides the tufted hairs there are thick-walled unicellular 

 hairs, resembling the rays of the tufted hairs, in Pavonia arabica. 

 External glands occur on young branches and have the same charac- 

 ters as of those on the leaf. 



The primary cortex is characterised by subepidermal cork in 

 Sida grewioides, Abutilon fruticosum (fig. 56) and Gossypium herba- 

 ceum (fig. 60). Collenchyma occurs in the cortex in all members ; 

 it may form long strands as in Pavonia arabica or a continuous ring 

 as in other species. Assimilatory tissue consists of palisade cells in 

 Hibiscus micranthus (fig. 54) ; in other species it is formed of 

 chlorenchyma. 



The pericycle is composed of closely placed rhomboidal groups of 

 stone-cells ; it is reduced on the lower side of the inclined branches 

 of Hibiscus micranthus. There are numerous small groups of bast 

 fibres in the soft bast of Sida grewioides and Pavonia arabica. 



The wood forms a composite hollow cylinder in all members. 

 The vessels are small and arranged in closely placed rows. The 

 interfascicular wood prosenchyma is not very extensive. The medull- 

 ary rays are uniseriate in Sida greioioides and Pavonia arabica ; in 

 others they are 1-3 seriate. In Abutilon fruticosum there occur 

 vascular bundles in the pith close to the xylem cylinder. On a small 

 portion of the axis in Pavonia arabica, Hibiscus micranthus and 

 Gossypium herbaceum the wood is reduced ; in this portion of the 

 axis the wood is much narrowed and vessels are few and small. 

 This may be accounted for by the inclined nature of the axis, the 

 wood being reduced on the lower side. 



The pith consists of thick-walled cells in Abutilon fruticosum ; 

 it is composed of thin-walled cells in others. 



Internal glands occur in the cortex in the form of secretory 



