32 BULLETIN 824, U. S. DEPARTMENT OF AGRICULTUEE. 



achenes, or fruits, still attached to the receptacle, or, very often, 

 fallen out, depending upon the ripeness of the heads. Consequently 

 appreciably little of the achene or fruit tissues is found in closed- 

 flower powder, while powder ground from open flowers is rich in the 

 lignified tissues of the fruit and quite devoid of pollen grains. 



Stem tissues occur in all powders to some extent, although they 

 should not be present in excessive amount. Careful study of the 

 stem tissues and the tissues of the flower head wUl show that there 

 is not the slightest difficulty in distinguishing between them. 



The following references in the bibliography (p. 83) deal with this 

 subject: 23, 24, 29, 47, 69, 106, 115, 116, 117, 118, 119, 137, 148, 150, 

 152, 156, 162, 163, 169, 174, 186, 199, 202, 246, 249, 257, 258, 261, 

 278, 279, 281, 282, 285, 289. 



CHEMICAL METHODS. 



In all of the pubhshed work relating to the chemical analysis of 

 insect powder the determinations have been practically confined to 

 those of ash and of ether-soluble material, together with specific tests 

 for tiu-meric, lead chromate, and other adulterants, the presence of 

 which might be suspected. The active principles of the powder 

 being unknown^ a comparison of the contents of the ash, ether ex- 

 tract, etc., of the sample undergoing examination with those of 

 powders of known purity has afforded the only method of judging the 

 genuineness of a commercial powder by chemical means. 



The first published analyses of insect powders are those reported 

 in 1879 by Hilgard (131), who determined the ether extract of 4 

 samples with the results shown in Table 4. 



Table 4. — -Ether-extract content of insect powder {Hilgard). 



Ether 

 extract. 



'Persian Insect Powder" 



'Buhach" (sample grown in 1878) . 

 'Buhach" (sample grown in 1879) . 

 'Lyon's Magnetic Powder" 



Per cent. 

 9.5 

 6.1 

 5.8 

 4.9 



His tests of these extracts on insects showed that the amount 

 of the extract present was not necessarily a measure of the efliciency 

 of the powder. 



Grote (108), in 1880, found lead chromate in a sample of insect 

 powder. He regards the odor of an insect powder as furnishing 

 more evidence of its genuineness than the color. Krai (164), in 

 1880, found curcuma in a series of insect powders, but no lead chro- 

 mate. Howie (139), in 1883, reported the results of the chemical 

 examination of 12 insect powders. He considered the chemical 



