32 BULLETIN" 824, U. S. DEPARTMENT OF AGRICULTURE. 
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 will 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 published 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 turmeric, 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). 
Product. 
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 efficiency 
of the powder. 
Grote (108), in 1880, found lead chromate hi 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), hi 
1880, found curcuma in a series of insect powders, but no lead chro- 
mate. Howie (139), hi 1883, reported the results of the chemical 
examination of 12 insect powders. He considered the chemical 
