MATERIALS 25 



syringe mentioned on p. 19. The quantity to be used 

 in such cases is from 2 to 4 ozs. to each tree, dis- 

 tributing this at three or four points at a distance of a 

 foot or two from the stems. The ground should not be 

 too dry at the time of appHcation, and the nozzle of 

 the syringe should be thrust down to about six inches 

 below the surface. In the vaporous condition, carbon 

 disulphide does not seem to injure the roots of plants, 

 but it does so when liquid, probably owing to the 

 intense cold produced by its evaporation ; conse- 

 quently, if the end of the injector is felt to strike one 

 of the roots, it should be withdrawn and inserted 

 elsewhere. 



Ants' nests may be destroyed by pouring half an 

 ounce of carbon disulphide into the nest through a hole 

 made in it, and then stopping up the hole. A second 

 application is needed about two weeks after the first, 

 as the sulphide does not seem to kill the pupae. 



Copper compounds. — With the exception of Paris 

 green, described above, the compounds of copper are 

 used as fungicides only. A great number of different 

 preparations have been investigated, some consisting 

 of the carbonate, but the majority of the sulphates in 

 some form or another. Copper sulphate itself can be 

 used only on trees when they are dormant, for it is 

 acid in its reaction, and destroys the leaves. For 

 summer use, therefore, the copper sulphate is con- 

 verted by the addition of lime into a basic sulphate, 

 which is insoluble, but which by the action of the 

 carbonic acid of the air, gradually liberates small 

 quantities of the ordinary sulphate, sufficient to act 

 on the fungi, but not sufficient (as a rule) to result 



