CLASSES OP INSECTS. 107 



those which yield volumes of steam as well as smoke, so 

 that masses of wet straw or rubbish, placed over dry stuff 

 enough to maintain combustion, are the best material. 

 Running or standing water close to the plants will also 

 prevent frost effect, providing the temperature does not 

 sink very far below the freezing point, nor remain there 

 too long. Under such conditions, covers of paper, bur- 

 laps, etc., also serve a good temporary purpose. More ef- 

 fective protection is described in the chapter on propaga- 

 tion. 



INJURIOUS INSECTS AND FUNGI. 



It should be borne in mind that the attacks of these 

 evils are in many cases conditioned upon weakness and un- 

 thrift to the plant, and the danger from both insects and 

 blights is reduced by keeping the plants in most active and 

 vigorous growth. Lack of cultivation, lack of plant food 

 in the soil, and lock of moisture, are invitations to these 

 invaders. The natural resistance of the plant is broken 

 down, and it becomes a prey to its enemies. But the best 

 growing conditions do not render plants immune against 

 all pests. Some are so aggressive that the grower has to 

 fight to save his crop, and to fight hard sometimes. 



Fortunately, warfare against insects has been greatly 

 simplified during recent years by the use of remedies of 

 comparatively recent application. There are two chief 

 divisions of insects : -first, biting insects, which are recog- 

 nized by the gardener by the fact that they make holes 

 in the foliage ; second, sucking insects, which make no holes 

 but pierce and extract the sap in such a way that the leaf 

 wilts, loses color and perhaps dies without losing any ap- 

 preciable part of its surface. Each of these classes has 

 its own remedy. 



Remedies for Biting Insects. Insects which consume the 

 leaf surface are destroyed by poison, and this can be 

 used in such minute quantities as not to destroy the fo- 

 liage nor render it dangerous for food purposes unless 

 the plant is nearly in condition for eating, and then, of 



