666 



SCIENTIFIC AND APPLIED PHARMACOGNOSY 



secretory cells are also found in a number of genera. The walls 

 of the trachese possess either simple pores or occasionally scalariform 

 perforations. The wood fibers are marked by simple pores. The 

 non-glandular hairs are usually uniseriate. The glandular hairs 

 are widely distributed and polymorphic. The stomata are usually 

 surrounded by 3 or more epidermal cells. Calcium oxalate is secreted 

 occasionally in the form of small needles or octahedra, and very rarely 

 in the form of rhombohedra or rosette aggregates. 



ARNICA. Arnica Flowers. The dried, expanded flower-heads of 

 Arnica montana (Fam. Compositse), a perennial herb indigenous to 

 central Europe, and growing in the mountains of Switzerland, Asia 

 and western North America. On account of the involucre and torus 



FIG. 293. Arnica florets: A, overlapping, bristly hairs of pappus; B, ray or 

 ligulate floret; C, disk or tubular floret. AC, inferior ovary becoming in 

 fruit an achene; PA, pappus; P, corolla; A, anthers; Y, style; T, bifid 

 stigma. 



being injured by the larvae of the insect Trypeta arnicivora, these 

 parts are removed and the florets alone used. 



Description. Sub-globular or truncate-conical, about 15 mm. 

 in diameter; involucre campanulate, bracts twenty to twenty-four 

 in two rows, linear-lanceolate, dark green, pubescent glandular; 

 torus solid, slightly convex, deeply pitted, bristly hairy; ray or lig- 

 ulate florets (Fig. 293), fourteen to twenty, about 2 cm. in length, 

 bright yellow, pistillate, corolla 3-toothed, 7- to 12-veined, very 

 pubescent and glandular below, ovary about 4 mm. in length, erect, 

 pubescent and glandular, pappus consisting of a single row of about 

 thirty rough bristles; disk or tubular florets (Fig. 293), forty or fifty, 

 about 17 mm. in length, perfect, bright yellow, corolla 5-toothed, very 



