OCCURRENCE OF MANGANESE IN INSECT FLOWERS 
AND INSECT FLOWER STEMS 
By C. C. McDonnell, Chief t and R. C. Roark, Assistant Chemist , Insecticide and 
Fungicide Laboratory, Miscellaneous Division, Bureau of Chemistry , United States 
Department of Agriculture 
INTRODUCTION 
While working on chemical methods for the detection and estimation 
of powdered pyrethrum stems in insect powder (pulverized flower heads 
of Chrysanthemum {Pyrethrum) cinerariaefolium Vis.), the writers noted 
that Unger (14, 15) 1 proposed a method of determining whether a 
powder was strongly adulterated with stems by testing it for manganese. 
He stated that pyrethrum stems contained no manganese, while it was 
always present in the flowers. Thoms (13) found manganese in the 
ash of C. leucanihemum and P. indicum , both of which have been used 
to adulterate insect powder, and Jiittner and Siedler (7, p. 411) showed 
that pyrethrum stems from Dalmatia are not entirely manganese-free; 
but, inasmuch as none of the above investigators determined manganese 
quantitatively, it seemed worth while to test Unger’s method more 
thoroughly. Furthermore, the present writers desired to test what effect 
the presence of manganese would have on the content of phosphoric acid. 2 
They have devised a method 3 for the determination of powdered stems 
in insect powder, which is based partly on the difference in the phosphoric- 
acid content of the stems and flowers, and it was essential to know 
whether the presence or absence of manganese would affect this ratio. 
The object in this investigation, therefore, has been twofold: (1) The 
exact estimation of manganese in the stems and flowers of C. cinerariae¬ 
folium from different countries in order to determine whether this element 
is constantly present in a greater degree in the flowers than in the stems, 
or vice versa, and (2) to determine what effect the presence of manganese 
has on the phosphoric-acid content. 
PREVIOUS INVESTIGATIONS ON THE CONTENT OF MANGANESE IN 
PEANTS 
It is not the purpose here to review all published work pertaining to 
the presence of manganese in various plants, but rather to refer to a 
few investigations bearing more directly on the problem with which the 
writers have been engaged. 
1 Reference is made by number to “ Literature cited,” p. 82 . 
2 Kelley (8, p. 39) states that plants grown on highly manganiferous soil contain less phosphoric acid 
than the same plants grown on a soil containing only small amounts of manganese. 
8 Not yet published. 
Journal of Agricultural Research, 
Washington, D. C. 
kg 
(77) 
Vol. XI, No. 3 
Oct. 15,1917 
Key No. E—7 
