80 
BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE. 
were more active than the mature or "open" flowers. In the trade, 
insect flowers are divided into 3 grades: "Closed," "half-closed," 
(or "half-open"), and "open." The "closed" flowers are usually 
sold for about twice as much as the "open" flowers, which would 
imply that their insecticidal power is correspondingly greater. 
Of those who have conducted investigations on the active principle 
of insect flowers, Gerard (93) is the only one who states in what part 
of the flower it is chiefly found. According to him, there are 2 active 
substances, an oleoresin and an essential oil, which are found princi- 
pally around the ovaries of the flower, and to a small extent in the 
corollas. 
The work on insect flowers and stems here reported, in which it is 
shown that the nitrogen content increases with the grade of the 
product, led to a determination of this constituent in the different 
parts of the flower, and at the same time a test of these same parts 
on insects to see if the insecticidal effect was related in any way to 
the amount of this element present. Some typical commercial 
"open" flowers (C. cinerarisefolium) were obtained, and dissected 
into their principal parts. In most commercial samples, the greater 
number of the flowers have lost their disc and ray flowers, and con- 
sist only of fruit receptacles, and involucral scales. The fruit 
amounted, on the average, to 80.5 per cent, the receptacles to 10.8 
per cent, and the involucral scales to 8.7 per cent of the whole 
flowers. Enough disc flowers were collected to determine their 
nitrogen content, but these were lacking in so many of the "open" 
flowers that their natural relative proportion could not be determined. 
Their normal actual percentage by weight, however, is very small. 
The results of the analyses are given in Table 47. 
Table 47. — Determination of nitrogen content of insect flowers. 
Sample. 
Xitrogen. 
Percentage 
of total 
nitrogen. 
Entire open flower 
Per cent. 
1.26 
1.40 
.67 
.51 
1.68 
Fruit 
89.4 
5.7 
Involucral scales 
3.5 
The nitrogen in the fruit of 5 other samples of "open" flowers 
was also determined, with the following results: 
Table 48. — Nitrogen in fruit and flowers of insect flower plants. 
Fruit. 
Entire "open" 
flower. 
Per cent. 
1.34 
1.32 
1.34 
1.24 
1.26 
Per cent. 
1.31 
1.22 
1.28 
1.25 
1.25 
