24 
BULLETIN" 824, TT. S. DEPARTMENT OF AGRICULTURE. 
Trottner (278) has worked out a method in which the value 
of an insect powder is determined by estimating the number of 
pollen grains in 1 milligram of the sample. His results, however, 
vary greatly, as shown in Table 3, which summarizes all of his re- 
ported determinations. 
Table 3. — Number of pollen grains per milligram of insect powder. 
Product. 
Closed flowers of C. cinerarisefolium pulverized in a mortar 
Do 
Open flowers of C. cinerarise folium pulverized in a mortar 
Do 
Do 
Commercial powder ground from closed flowers (Riedel) 
Commercial powder ground from open flowers (Riedel) 
Commercial powder ground from closed flowers (Caesar and Loretz) 
Commercial powder ground from half-closed flowers (Caesar and Loretz) . . . 
Commercial powder ground from open flowers (Caesar and Loretz) 
Commercial powder ground from closed flowers (Schuchardt) 
Commercial powder ground from half-closed flowers (Schuchardt) 
Commercial powder ground from open flowers (Schuchardt) 
Commercial powder (Apothecary A) 
Commercial powder ground from wild closed flowers (Apothecary B) 
Commercial powder (Apothecary C) 
Commercial powder ground from cultivated closed flowers (Apothecary D) 
Commercial powder (Apothecary E) 
Pulverized closed flowers of P. roseum 
Pulverized open flowers of P. roseum. 
Flores Pyrethri rosei, pulvis No. (Gehe and Co.) 
Flores Pyrethri rosei, pulvis No. 1 (Gehe and Co.) 
Pollen 
grains in 1 
milligram. 
2,881 
2,159 
545 
210 
151 
3,066 
158 
2,255 
920 
785 
4,402 
5,544 
1,319 
2,071 
1,235 
1,176 
575 
550 
4,721 
2,264 
5,741 
Morphology of Whole Insect Flowers. 
The flowers usually employed in the production of insect powder 
or Pyrethrum powder are derived from either the Dalmatian or the 
Persian insect flowers, botanically known as Chrysanthemum cine- 
rarisefolium (Trev.) Boca and Chrysanthemum roseum Web. & Mohr., 
respectively. The Dalmatian flowers compose the greater part of 
the commercial insect powders, the Persian flowers being rarely seen 
in commerce at the present time. Of recent years, Japanese insect 
flowers have been coming into the market. According to one 
authority (24) the form known as Chrysanthemum indicum, with a 
yellow ray flower, is widely spread through China and Japan, while 
in the mountains of Hupeh occurs a white or pink rayed form, which 
has been named Chrysanthemum morifolium. Dr. Henry, who has 
collected specimens which are in the Kew herbarium, considered 
these two wild plants the probable progenitors of the cultivated 
strains. As far as histological characters are concerned, the Japanese 
flowers can not be distinguished from Chrysanthemum cinerarise- 
folium. 
A review of the literature has shown that some little work has 
been done on the morphology of the whole insect flowers. The 
descriptions to follow are condensed reviews of the most important 
articles. They are somewhat abbreviated for the reason that the 
literature already contains numerous descriptions of the flowers, 
