THE EPIDERMIS AND PERIDERM 67 



their arrangement, their size, their color, the character of their 

 walls, whether rough or smooth, whether branched or non- 

 branched, whether curved, twisted, straight, or twisted and 

 straight, whether pointed, blunt, or forked. 



FORMS OF HAIRS 



PAPILLA 



Papillae are epidermal cells which are extended outward in 

 the form of small tubular outgrowths. 



Papillae occur on the following parts of the plant: flower- 

 petals, stigmas, styles, leaves, stems, seeds, and fruits. Papillae 

 occur on only a few of the medicinal leaves. 



The under surface of both Truxillo (Plate 6, Fig. 3) and 

 Huanuca coca have very small papillae. The outermost wall of 

 these papillae are much thicker than the side walls. The papillae 

 of klip buchu (Plate 6, Fig. 4), an adulterant of true buchu, has 

 large thick-walled papillae. 



The velvety appearance of most flower-petals (Plate 6, 

 Figs. 2 and 5) is due to the presence of papillae. The papillae 

 of flower-petals are very variable. In calendula flowers (Plate 

 6, Fig. i) they are small, yellowish in color, and the outer wall 

 is marked with parallel striations which appear as small teeth 

 in cross-section. The ray petal papillae of anthemis consist of 

 rather large, broad, blunt papillae with slightly striated walls. 

 The papfllae of the ray petals of the white daisy consist of papillae 

 which have medium sized, cone-shaped papillae with finely striated 

 walls. The papillae of the flower stigma vary greatly in different 

 flowers. In some cases two or more types of papillae occur, 

 but even in these cases the papillae are characteristic of the 

 species. 



The papillae differ greatly in the case of the flowers of the 

 compositae, where two t^-pes of flowers are normally present — 

 namely, the ray flowers and the disk flowers. 



In all cases observed the papillae of the stigma of the ray 

 flowers are always smaller than the papillae of the stigma of the 

 disk flowers. It would appear from extended observation that 

 the papillae of the ray flower stigma are being gradually aborted. 

 The papillae of the style are always different from the papillae 



