212 



BOTANY AND PHARMACOGNOSY. 



In the COROLLA the epidermal cells are generally more or less 

 centrifugally developed, forming prominent papillse (Fig. ii8, 

 A, B), which give the petals a velvety or satiny appearance, as in 

 the rose ; glandular and non-glandular hairs are also developed 

 which are peculiar to the corollas of irregular flowers, as in La- 



FiG. ii8. Inner morphology of the flower as illustrated in Viola tricolor. A, epider- 

 mal cells from the outer surface of the spurred petal showing papillae; B, epidermal cells 

 from the under surface of the petals, some of the cells showing centripetal thickenings, the 

 two without thickenings covering sub-epidermal mucilage-cells; C, epidermal cells from 

 the under surface of the petals showing a zigzag outline and short centripetal thickenings; 

 D, surface view of the mesophyll of the petals; E, corkscrew-like hair from the inner sur- 

 face of the spurred corolla near the throat; F, a hair from the edge of an anther; G, epider- 

 mal cells of the anthers; H, surface view of the mesophyll cells from the spurred stamen 

 showing collenchymatous thickening; I, surface view of cells of endothecium; K, pollen 

 grain viewed from the side; L, pollen grain examined in water; M, pollen grain observed 

 in chloral solution. 



vandnla vera (Fig. 285, A) and Viola tricolor (Fig. 118, ) ; 

 stomata are comparatively few in number. The epidermal cells 

 are but slightly cutinized, and in surface view are strongly undul- 

 ate and appear striate owing to the papillose development (Fig. 



