497 



ground. In other words, supposing one injection is made in every 

 square yard : 4,840 square yards multiplied by 10 grammes equals 

 48'4 kilogrammes, or 95'51b., are injected per acre. With one ring 

 added, 9 grammes are injected, or ^ less ; with two rings 8 

 grammes only are injected ; and so on, each additional ring added 

 decreasing the dose by T ^. 



The apparatus having received a charge of bi- sulphide of 

 carbon, is easily thrust into the ground by pressing on the handles, 

 S, and the spur P. The knob, JS , is then pressed down, and a 

 dose of the liquid injected into the ground. On removing the 

 needle the operator stops the hole left in the soil with his heel, 

 and the volatile insecticide, being thus imprisoned in the soil, 

 diffuses through it, penetrates every cleft and rent, and reaches 

 the enemy, which it soon suffocates. The eggs, however, are not 

 destroyed, and a fresh application after hatching, and within a 

 fortnight, has to be made to entirely rid the ground of the pest. 



According to the degree of intensity of the invasion, one or 

 two injections per square yard are made, or, in other words, the 

 knob of the piston is pressed down two or three times. 



Between the lines the steel needle is thrust in full length into 

 the ground, viz., 8 to 10 inches, but nearer to the stocks half that 

 depth is sufficient. 



Bi-sulphide of carbon is used with best advantage in porous 

 soils, whilst on heavy clays, or in shallow soils with a clay subsoil, 

 at a depth of 10 to 12 inches, its application is not attended with 

 the best results, as the insecticide cannot permeate through the 

 mass of the ground, and by being brought into direct contact with 

 the roots proves injurious to the plant. 



HOW AND WHEN TO SPRAY. 



Credit is due for much of the information contained in this 

 chapter to the contributions of Dr. N. A. Cobb, the Pathologist of 

 the Department of Agriculture, Sydney, and published in the 

 Agricultural Gazette of N.S.W. 



Mature plants wear an armour of dead cells. These repre- 

 sent the outside skin or cuticle which lines the upper and under 

 surface of the leaves, and afford protection to the more tender cells 

 which underlie them. 



When observed under a microscope they are not unlike a thin 

 parchment or small scales of bark. Owing to their presence, 

 wind, rain, sun, or dust have no action on the more delicate 

 internal living cells, which would soon be destroyed by handling 

 or exposure were it not for this natural jacket which covers 

 them. This jacket or covering is not, however, absolutely con- 

 tinuous, and small microscopic breathing-pores or stomata occur 

 at intervals on the surface. 



Let us suppose such a leaf to be attacked by a fungus para- 

 site. If thin shavings of such a diseased leaf were cut bv means 



