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 "hali-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 {G. 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. 



Nitrogen. 



Percentage 

 of total 

 nitrogen. 



Entire open flower 



Per cent. 

 1.26 

 1.40 

 .67 

 .51 

 1.68 





Fruit 



89.4 



Receptacles 



5.7 



Tnvnliinrnl si^a.les. 



3.5 



Disc flowers - - - - - - - - - - 











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 



