RELATIONS OF BOTANY TO AGRICULTURE. 433 



to soak the seed-grain, just before sowing, in a solution of sul- 

 phate of soda; then to mix the moist grain with caustic lime, by 

 which the plants or their spores are destroyed, if present. 



Ergot is the distorted and diseased seed or grain of rye, and 

 sometimes of other grasses, caused by the attacks of a fungus, 

 and is exceedingly poisonous to both men and animals. It is not 

 so likely to occur on well-drained land as on that which is wet. 



Rust is a disease attacking grains and grasses, and occasionally 

 other plants, and is found to be caused by the development of 

 minute fungi in the cellular tissue of the floral bract, or chaff', and 

 the leaves. It weakens the plant, and often renders the grain 

 crop worthless. The growth of different fungi seems to depend 

 largely upon the state of the weather, — whether dry, moist, or 

 variable in temperature, — and is therefore difficult to control. 

 Something in addition to what has been suggested may be done 

 against these enemies by a judicious rotation of crops ; by the 

 selection of the most suitable varieties of seed ; by improved 

 methods of cultivation ; or by removing from fields, ditches and 

 hedgerows all those plants which support these injurious fungi, 

 and so perpetuate them. 



Another very destructive form of fungus develops in woody 

 fibre, in close, damp places, producing "dry rot." This is so 

 prevalent in some parts of London that wood-work in houses has 

 to be renewed every ten or twelve years. This form of fungus 

 may be checked in its ravages by saturating the wood with some 

 metallic poison, as corrosive sublimate, or chloride of zinc. Fungi 

 likewise often penetrate the wood of fruit and forest trees, begin- 

 ning where wounds have been made, and gradually causing the 

 death and decay of the entire mass of timber. In many cases, 

 timber apparently sound, cut from dead trees, will be found on 

 examination to be permeated by the mycelium of some fungus 

 which on exposure to air and moisture will develop and destroy 

 its durability. The growth of fungi on fruit which has been 

 bruised or injured by insects, is one of the most common causes 

 of decay. Experiment has shown that a sound apple, inuoculated 

 with fungus from a decaying one, may be destroyed in three days, 

 and its tissue filled with the cells of the destroyer. The obvious 

 remedy is extreme care in sorting, handling and storing the fruit. 



Time would fail us to. recount the damages inflicted upon the 



husbandman, and so upon the race, by these almost invisible, but 



innumerable and relentless foes. It must answer our present pur- 

 28 



