146 POWDERED "VEGETABLE DRUGS 



so as to indicate clearly the nature of the article. The qualifying 

 word or phrase should appear in type sufficiently clear and in position 

 sufficiently prominent to attract the immediate attention of the pur- 

 chaser. In a case of this kind, where the constituent substances are 

 named, the predominating substance should be named first in order. 



The following is recommended as the official description of insect 

 powder: 



Insect Powder. Pyrethrum Insect Powder. 



Made from the flower heads of Chrysanthemum cineraricefolium 

 Bocc., C. roseum Web. and Mohr, and C. Marshallii Ashers. 



Fine powder, ranging from No. 80 to fine meal. 



Rather dull yellowish brown color. 



Somewhat aromatic odor, faintly recalling chamomile. 



Bitter and somewhat pungent taste. 



The histological characteristics (microscopical) of the three official 

 species of Chrysanthemum are closely similar. Vascular and paren- 

 chymatous tissues are not characteristic. T-shaped trichomes (the 

 basal cells usually broken and removed, leaving the double tapering 

 pointed, soft, flexible, somewhat bent and twisted, rather thick-walled 

 colorless, end-cell plainly to be seen) are the most characteristic 

 structures. Amount of fibrous tissue (ducts, tracheids, sclerenchyma- 

 tous elements) is in direct proportion to the amount of stem tissue 

 present. Amount of sclerenchyma cells and clusters (typical cell 

 forms, singly and in groups) is in direct proportion to the amount of 

 matured (old) flower heads present. Pollen grains should be abundant 

 and show the general structural characteristics of the pollen grains 

 of the flowers belonging to the natural order Compositse, that is, they 

 are spherical with numerous distinct conical projections of the exine, 

 and yellowish brown in color when mature. 



Pyrethrum insect powder should contain not less than 2,500,000 

 pollen grains per gram of the air dry powder; or, should show at least 

 an average of two pollen grains per field of the high power (No. 2 

 ocular and No. 7 objective), or, 20 grains per field of the low power 

 (No. 2 oc. and No. 3 obj.) of the compound microscope. Lignified 

 (showing red coloration with HC1 and phloroglucin) fibrous elements 

 (in clusters) and sclerenchyma cells (single cells and in clusters) 

 must not exceed 50 per cent, of the entire mass of the powder, as 

 estimated ocularly under the compound microscope. Ash should not 

 exceed 8 per cent. 



A high grade insect powder is made from the partially expanded 

 flower heads of the official species of Chrysanthemum, and would show 

 the following microscopical characteristics: 



