Rust or Mildew. 229 



than others. Is it in the location, exposure, soil or climate? 

 Each of these may have a tendency to promote it in different 

 seasons and under certain conditions. 



The facts bearing on this subject, as drawn from observations 

 the past season are, that up to the 11th of June everything was 

 favorable for a healthy growth of tree and a large and fine crop 

 of fruit. Up to this date the weather had been moderately warm, 

 clear and dry, but at this time a change came, showers were fre- 

 quent, the air was hot, and a hot wind set in from the south and 

 southwest and blew hard all night, raising the thermometer to 90° 

 in the day and keeping it up high during the night, and in the 

 morning the bright, fresh look of vegetation had disappeared ; 

 everything was wilted and drooping ; then came a rather cold 

 rain, which was in turn followed by a few days of moderately 

 cool weather, when these spots first made their appearance on the 

 leaves and fruit. In addition to this, the hot, dry air, before the 

 rain came, had so exhausted the moisture in the leaves, that they 

 shriveled up, so that the edges and the tops of the tender twigs 

 were turned black or brown. In some instances the effect was 

 so great that they were wholly dried up and dead, and when 

 favorable weather returned, growth was checked until new buds 

 and leaves were developed. As the principles and manner of 

 vegetable growth are similar in the different forms of plant life, 

 the result was about the same in trees, grains and grasses. 



The way in which this injury was done will be more clearly 

 seen, if we briefly consider how plants feei and their growth is 

 made. The sap taken up from the earth by the roots passes up- 

 ward from cell to cell, mainly in the new wood growth, deposit- 

 ing in them in its passage more or less of starch and other earthy 

 elements, until it reaches the cellular structure of the leaf in a 

 diluted and weakened condition. In passing through the cellular 

 structure of the leaf, it gives off the excess of moisture and ab- 

 sorbs oxygen, carbonic acid and ammonia from the atmosphere, 

 through myriads of mouths, situated both on the upper and under 

 sides of the leaf. The sap thus vitalized passes down bstween 

 the sap-wood and bark, perfecting the auxiliary buds and devel- 

 oping a new growth of woody fibre from the leaf to the root. 



