12 SCIENCE AND FRUIT GROWING 



FUNGI * 



A fungus is a plant of the lower order (Cryptogams), which 

 differ from the higher plants by possessing no flowers, and by 

 producing none of the green colouring matter (chlorophyll) which 

 characterises the leaves of ordinary plants. It forms seeds, 

 however, known as spores, and also roots, in the form of exceed- 

 ingly fine filaments (hyphae), known as the mycelium, or, more 

 commonly, as spawn. It is this mycelium by which the damage 

 is done to trees attacked by a fungus; the hyphse make their 

 way through the wood, etc., breaking down the cells of which it 

 is composed, and thus destroying the plant. This renders it 

 practically impossible to apply any remedy once a tree has been 

 invaded by a fungus, unless we can remove the whole of the part 

 attacked ; and our efforts, therefore, must be directed to prevent- 

 ing the fungus from seeding, and propagating elsewhere. 



The seeds, or spores, which are microscopic in size, are produced 

 in several ways. The mycelium itself in some cases becomes 

 converted into a chain of spores, but the more usual process is 

 for it to send out a number of branches, each bearing at its end 

 a spore, or a receptacle containing many spores (conidia spores). 

 The summer spores of a fungus are formed in this way, and the 

 masses of spore-bearing filaments or branches produce the appear- 

 ance of a downy covering over the object attacked, familiar to us 

 in the form of mildew or mould. The branches and spore recep- 

 tacles constitute, in the larger fungi, the portion of the plant 

 which is commonly called the fungus itself, such as the puff-ball, 

 mushroom and toadstool. 



The mycelium of a fungus also produces other spores, known as 

 perithecia, which are often formed inside the host plant, and these 

 are enclosed in a tough, leathery receptacle, which renders the 

 destruction of them very difficult. These are the winter, or 

 resting spores, and they are capable of resisting the most intense 

 cold without being injured, and may remain unchanged for years, 

 starting into activity only when they find themselves placed 

 under favourable circumstances. This, as a rule, is in the spring. 



A fungus, however, besides reproducing itself by means of 

 spores, does so, also, more directly by means of its mycelium, 

 parts of this becoming changed, and hardened into what is called 

 sclerotia, in which condition it passes the winter, and develops 

 in the following year, spreading itself through the soil, and 

 attacking fresh plants. 



1 This description of fungi, and that of insects, is borrowed from 

 Fruit Trees and their Enemies, by Pickering and Theobald. 



