226 



bases have no power of arresting although they may retard their pro- 

 gress. Boiling- water, also, for a time arrests the progress of fungi. A 

 knowledge of the habits of fungi and of the substances and conditions 

 which retard or foster their growth will, to some extent, enable fruit- 

 growers to modify fungus blight. But independent of all chemical ap- 

 pliances, drainage, and sheltering by belts of timber or hedges, would 

 be of great importance, when the land or orchard is devoid of natural 

 sources of protection. It is not simply to the conditions of high or low 

 temperatures, or to the hygrometric state of the weather that blight, 

 rust, molds, &c., owe their origin, but to a combination of many condi- 

 tions. Heavy rains on "well-drained soil will not present the same con- 

 ditions to vegetable growth which they would on poorly drained. A 

 favorable condition of soil and climate is required by foliage of spring, 

 summer, and autumn, for a healthy performance of its functions. Under 

 highly favorable conditions of climate and soil the wood becomes ma- 

 tured and, consequently, the fruit and the leaves drop when, and only 

 when, the uses for which they were formed have been accomplished. 

 The wood of every tree when fully matured has condensed the sap, 

 forming it into wood or other solid material ; consequently, the cells 

 under such conditions are comparatively emi)ty, and have room for the 

 expansion of any limited portions of sap remaining. Climatic derange- 

 ment in the animal as well as in the vegetable economy is frequently 

 produced from sudden changes of temperature. A mantle of ice, or of 

 snow, will not necessarily prove hurtful to plant-life ; flowers are some- 

 times found blooming under snow. It is from the unprepared condition 

 of plants and trees that injury from frost mostly spring. It is not un- 

 usual for a shepherd on the mountains of Scotland, while tending his 

 sheep to save them from perishing in snow-drifts, to immerse his plaid 

 in a brook, wring it out, and wrap it round himself. It freezes, and ice 

 being a non-conductor of heat, he is kept warm in his frozen mantle. 

 The Laplander lives in huts of ice or snow to shield himself and family 

 from the bleak winds of winter. Ice, snow, and water, are classed as 

 non-conductors. It is when water is converted into vapor that the 

 body from which it evaporates becomes cold. Millions of pounds of 

 parafSne have been for a long period annually extracted from coal-oil by 

 taking advantage of this principle ; by the evaporation of eth'ev in con- 

 tact with a vessel containing coal-oil the paraffine freezes solid in the 

 oil and is thereby easily removed. But it is not the cold, properly con- 

 sidered, which produces the disease owing to the bursting of plant-cells ■ 

 but to the stoppage of the functions of assimilation in the presence of 

 myriads of germs of fungi and infusorial life. Healthy plants will de- 

 compose any foreign substance suitable as food and assimilate it in the 

 sup])ort of their own function. 



"Fungi consists of two principal elements, the vegetative and the fruc- 

 tifying. If we take, for example, the common mushroom, the vegeta- 

 tive is represented by the spawn which, for a time, carries on all exist- 

 ing functions of the plant; the fructifying by the stem, with the cap 

 and gills which bear nearly the same relation to the spawn as the flower 

 with its various organs to the stem on which it grows. The spawn may 

 flourish for years without bearing any fruit, but fruit can never be pro- 

 duced without spawn." 



The spawn of fungi, whether in a cellular or fillamentous condi- 

 tion, undergoes an infinite variety of modifications ; it is developed in 

 various situations, and even when present beyond a doubt among the 

 tissues of plants, at whose expense it lives, is very dilficult to detect, 

 in consequence of its extremely minute condition. 



