DETECTION OF ADULTERATION. 29 



that is, the individual segments of the periphery are but little dis- 

 torted or curved. The walls are thin and have a slight beading due 

 to deep, broad, regular pits, while the corners come down to quite 

 sharp definite angles. There are present an abundance of horn- 

 shaped hairs (trichomes) from 50/t to 400/* long and from 35/* to 70/t 

 diameter at the base. Although the cavity in some of the.. hairs, 

 especially the smaller ones, is simple, in many of them it is divided by 

 transverse septa into two or three chambers. The epidermal cells 

 adjoining each trichome are commonly from 8 to 14 in number, 

 though these limits are at times exceeded. They are much smaller 

 in average size than those of the intra-trichome regions. The cells of 

 the under epidermis (PL I, fig. 2) are somewhat smaller than those of 

 the upper epidermis, and the walls are much more bent or curved, 

 giving the cells very irregular outlines. The beading of the walls is 

 of about the same prominence as in the upper surface. On the under 

 surface are two kinds of trichomes: (1) horn-like forms similar to 

 those on the upper surface but usually longer; (2) glandular forms of 

 from 3 to 4 cells, raised on a single-celled stalk, the whole forming a 

 club-shaped structure. The horn-like trichomes of both the upper 

 and lower sides of a leaf have commonly a slightly warty surface. 

 The lower epidermis is also furnished with many stomata or breathing 

 pores, but there is no such regularity in the number and arrangement 

 of the adjacent epidermal cells as in the case of the lentiscus. Rosette 

 crystals of calcium oxalate are often visible in the leaf tissue when 

 viewed from either side, though some leaves show but few or none. 

 An excess .of stems is detected by the presence of fibrous tissue in 

 greater amount than in good normal samples. Many fragments of 

 the powdered sumac leaf will show only the trichome scars, since in 

 grinding they are frequently broken off. 



LENTISCUS (Pistacia lentiscus). 



The method of clearing by chloral hydrate has a tendency to pro- 

 duce clearer tissue in P. lentiscus, than with R. coriaria. Both sur- 

 faces of P. lentiscus are free from trichomes. The upper epidermis 

 (PL II, fig. 1) is made up of cells having very conspicuous walls. 

 The outlines of the walls are straight and at the angles, instead of 

 coming down to sharp points, are slightly rounded, giving to them 

 a very distinctive appearance and one not to be confused with the 

 surface appearance of R. coriaria or any of its other common adul- 

 terants. This point is not so clearly shown in the photomicro- 

 graph as in the specimens themselves since this feature was subor- 

 dinated to producing the best general effect, the latter being much 

 more important in its identification. The cells vary in width from 

 17 /* to 30/*. 



117 



