No. 4.] 



INSECTICIDES. 



367 



on leaves depends on the destruction of the living contents 

 (protoplasm) of the cells which make up the leaf, as is 

 shewn by the illustrations which follow. 



Fig. 1 (original). Section through nor- 

 mal leal ol pig-nut hickory (Carya 

 porcina), showing structural element-. 

 E, epidermis; PC, palisade cells; SP, 

 spongy parenchyma; S, stoma or 

 breathing pore. 



Fig. 2 (original). Section through leaf 

 of same tree, "burned" by excess of 

 Paris green. Cell contents (proto- 

 plasm) of palisade cells and spongy 

 parenchyma dead and dried up; cell 

 walls shrivelled. 



HOW TO USE THESE POISONS AGAINST COMMON INSECTS. 



Spraying with a force pump is the best method of apply- 

 ing these poisons to trees. It is well to add from two to 

 four quarts of glucose or cheap molasses for every one hun- 

 dred and fifty gallons of the poison mixture" used, as this 

 causes the poisons to adhere to the foliage. To destroy the 

 bud moth (Tmetocera ocellana), spray when the buds begin 

 to swell ; against the codling moth ( Carpocapsa pomonella ), 

 spray just alter the petals have fallen from the blossoms. 

 The tent caterpillar (Ch'siocampa americana), the canker- 

 worms ( Anisopteryx pometaria^ Paleacrita vernata), as well 

 as the tussock moth (Orgyia leucostigma) and the elm-leaf 

 beetle (Galeruca xanthomelcena) t can be cleared from in- 

 fested trees by one or more thorough sprayings soon after 

 the insects make their appearance. 



Contact Insecticides. 



Against insects of the second group previously mentioned 

 (/. e., sucking insects) a ditl'erent means of attack must be 

 employed, for, as they do not take in solid nourishment, a 



poison applied on the foliage or stems, as in the case of 



