EXPERIMENTS WITH OTfiER EXTRACTS AND DECOCtlONS. 181 



a powder so alike in color and smell to Pyrethrum powder that the two 

 could not readily be distinguished. But however great this external 

 resemblance, the two differed widely in efficacy as insecticides. Dr. 

 Barnard, who, while still in Ithaca, New York, made some preliminary 

 trials with the alcoholic extract from the fresh or half dried flower 

 heads, wrote: 



"I have no evidence that the extract will prove of any practical 

 value, {ifter having atomized it on to many specimens of larval po- 

 tato-beetles, aphides, young grasshoppers, Mamestra picta, Fieris rapce^ 

 and other caterpillars." 



As to the experiments with the dry powder, Mr. Schwarz reports as 

 follows : " Ox-eye daisy powder was repeatedly applied to Cotton Worms 

 in the earlier part of October in the following forms: 1st, as dry pow- 

 der, mixed with flour, and undiluted; 2d, stirred up in water; 3d, as 

 alcoholic extract (made by repercolation) diluted with water and undi 

 luted; 4th, as tea; 5th, as a fume. In no instance even the slightest 

 effect on young or old worms was observed, though powder and fluids 

 were applied in large quantities and undiluted. The experiments were 

 all conducted with a view to ascertain the effect of the powder on the 

 worms by actual contact, and not by acting through the stomach. I 

 am also not prepared to say whether or not this powder has any eff'tict 

 on other insects; but there can be no doubt that if applied like pyre- 

 thrum, it is utterly worthless as a remedy for the Cotton Worm." 



Other experiments with infusions and decoctions made from the fresh 

 and dried flower heads and other parts of the plant, gave no better re- 

 sults, and every hope of obtaining in this plant a substitute for py- 

 rethrum had to be abandoned. 



EXTRACTS AND DECOCTIONS FROM VARIOUS PLANTS. 



That there are plants which contain volatile oils similar in effect to that 

 possessed by Pyrethrum, admits of little doubt. Professor Barnard 

 extracted from Bitter Almonds an oil which, upon experimentation, 

 proved to be equal or even superior to pyrethrum powder. However, 

 this oil is so expensive that no further experiments were made with it. 

 The vapor exhaled from the husk of certain South American nuts is 

 so strong as to be dangerous even to man, but we were not able to pro- 

 cure such to ascertain their effect upon insect life. The method prac- 

 ticed by European entomologists of killing microlepidoptera and other 

 delicate insects by the vapor emitted by laurel leaves also deserves men- 

 tion here. 



But few of our insecticides are, so far, drawn from the vegetable 

 kingdom, the most important of them being tobacco, hellebore, and py- 

 rethrum ; but there is a wide field in this direction for investigation. 

 The task of discovering among the multitude of plants such as may 

 possess insecticide properties is a difficult one, since we have little to 



