676 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



ish-green, finally changing to brownish-black. Nitric acid produces 

 a yellowish-brown color. The addition of ferric chloride to the pow- 

 der colors some of the fragments greenish-black. Outer epidermal 

 layer of the involucral scales consist of (a), polygonal cells, having a 

 striated cuticle; (6), numerous T-hairs consisting of a 2-celled stalk 

 and a horizontal needle-shaped unicellular summit; (c), sessile glan- 

 dular hairs, having a 2- to 8-celled secreting head. Fragments of 

 pistil show club-shaped, sessile, glandular hairs; small prisms of 

 calcium oxalate; and brownish-resin canals. Fragments of corolla 

 show elongated outer epidermal cells, having a striated cuticle, and a 

 few stomata, the latter being surrounded by 4 or 5 accompanying 

 cells. Inner epidermal cells of the corolla modified to papillae, the 

 walls on .surface view polygonal, the summit of the papillae appearing 

 as irregular circular central folds from which radiate the cuticular 

 folds or striations. The vascular bundles of the scales show lignified 

 sclerenchymatous cells and fibers. Fragments of achene show color- 

 less thin-walled cells of pericarp and rectangular, thick-walled, porous 

 and strongly lignified cells of the seed-coat, also a long, brown resin 

 canal, extending throughout the entire length of achene. 



Constituents. Insect flowers contain from a trace to 0.5 

 per cent of a volatile oil, the Persian flowers containing the larger 

 proportion, and the amount decreasing with the maturing of the 

 flowers. They also contain two resins, varying from 4 to 7 per cent, 

 the larger amount being found in the Dalmatian flowers; a small 

 quantity of a glucoside and a volatile acid. 



The toxic principle is Pyrethron, an amber-yellow, syrupy 

 substance which is the ester of certain unidentified acids, and on 

 saponification yields the alcohol pyrethrol which crystallizes in fine 

 needles. The acids combined in the ester pyrethron do not give 

 crystalline salts. 



Allied Plants. A large number of plants have been used as 

 insecticides. A list of these with reference to literature are given by 

 Roark (Amer. Jour. Pharm., 1919, 91, p. 25 and 91). 



Adulteration. The flowers of one or more of the Compositse are 

 substituted for or admixed with the genuine insect flowers. Of these 

 the following may be mentioned: Common field or ox-eye daisy 

 (Chrysanthemum Leucanthemum) ; and the yellow immortelle or 

 everlasting (Helichrysum arenarium). It is stated that sometimes 

 the entire stem with leaves are ground up with the flowers. Pow- 

 dered insect flowers, which are bright yellow in color, have usually 

 added to them powdered curcuma or chrome yellow (chromate of 

 lead). 



