LEAVES 269 



tals. In henbane, coca, and senna are found prisms. In bella- 

 donna, scapola, and tobacco leaves are found micro-crystals. 

 In most leaves no crystals occur. In witch-hazel and tea 

 leaves stone cells occur, but in most leaves there are no stone 

 cells. In eucalyptus, thyme, jaborandi, buchu, rosemary, and 

 white pine leaves are secretion cells; while in belladonna, 

 stramonium cells occur. In senna and coca leaves are crystal- 

 bearing fibres; most leaves do not have crystal-bearing fibres. 



In chimaphila and uva-ursi there are no outgrowths from 

 the epidermal cells. 



In senna, witch-hazel, chestnut, and coca, numerous non- 

 glandular hairs occur on the epidermis. In tobacco, belladonna, 

 henbane, pennyroyal, peppermint, and spearmint both glandular 

 and non-glandular hairs occur on the epidermis.. 



When studying leaves there should be considered the ab- 

 sence or presence of outgrowths and their nature; the nature of 

 the epidermis and, w r hen present, the number of layers of the 

 hypodermis; the nature of the stoma, whether raised above, 

 even with, or below the level of the epidermis; the number of 

 layers, and the distribution, when present, of the palisade 

 parenchyma; the form and amount of the spongy parenchyma; 

 the absence or presence of secretion cells; the nature and form 

 of the fibro-vascular bundles, and the nature and amount of 

 the organic and inorganic cell contents. 



