33 



ing a plant with poisons to protect it from these pests will readily be 

 seen. No matter how thick the poison may be, the insect's beak will 

 penetrate this poisonous layer, and it will take no food until the beak 

 has passed the limit of the poison and is deeply buried in the tissues of 

 the plant. 



" From the above it will be seen that : 



(a) To destroy chewing insects, such as the potato beetle, poison 

 must be evenly distributed over those parts upon which the insects 

 feed, and this may in some cases be done even before the insect is pre- 

 sent, or is visible. Only those poisons which cause death after being 

 eaten should be used. 



(b) To destroy sucking insects, such as plant lice, the materials must 

 be distributed upon the insects as evenly as possible and it is useless 

 to make any application before theinsect has appeared. Only those poi- 

 son which kill by coming in contact with the insect's body should be used. 



" First determine what kind of a pest it is that needs treatment, 

 then select the proper material. 



II. Upon Fungi. 



" Among fungi we find many serious enemies. It is difficult to tell 

 just what a fungus is, but some of the principal characteristics may be 

 mentioned. A fungus is a plant ; but unlike flowering plants, it 

 possesses no chlorophyll. Chlorophyll is the green-coloured protoplasm 

 found in flowering plants, and it is the only substance we know through 

 which plants change crude food to nutritive material. We must conclude, 

 therefore, that fungi do not prepare their own food, but feed upon 

 organic matter which is already adapted to their wants. They possess 

 no leaves, flowers, nor seeds. That part of any fungus which is of 

 most interest to the horticulturist is composed of long, fine threads, 

 either growing separately or in bundles ; these threads are known as 

 hypha?, and collectively they form the mycelium or vegetative portion 

 of the fungus. The mycelium corresponds to the roots and stems 

 of flowering plants. 



" Spores, which are organs performing the same office as the seeds 

 of flowering plants, are produced by this mycelium either directly, or 

 upon branches (sometimes called sporophores) which are thrown out. 

 These sporophores cause the white downy appearance seen upon grape 

 leaves affected with the downy mildew. A spore, strictly speaking, is 

 not a seed, for a seed contains a young plant, while a spore does not, 

 being usually composed of only one cell. If a spore finds the proper 

 conditions of heat and moisture it will germinate and send out a fine 

 filament, which, if nourished, grows on branches, and eventually a 

 plant like the original will be produced. 



"Most fungi in the North produce two kinds of spores, known as the 

 summer and the winter spores. The summer spores are usually borne 

 upon the exterior of the host-plant, or the plant on which the fungus 

 grows. These spores ripen quickly and propagate the fungus rapidly. 

 But if they do not germinate soon after ripening they lose their vitality. 



" The winter spores are usually produced within the tissues of the 

 host-plant, commonly in the leaves and fruit. They are the spores 

 which live through the winter ; but in the spring, under favourable 

 circumstances, they germinate, and thus the fungus is again developed. 



