Mr, W. Jones on the Mildew in JFhcat, 20 1 



It will be necessary for me to request the reader's attention to some particulars, 

 lespecting the mildew, that favour my hypothesis. The first is, that I believe it is 

 generally admitted to be produced by great dews ; and that dews having the same 

 relation to frost, as rain to snow, I have therefore considered frost to be the 

 the primary cause, and shall take unto my aid the following observations, not con- 

 fined to one year or two, but the experience of many ; thai it is at times discovered 

 in the leaf of the wheat plant in May, and from that time the stalk, either before or 

 after the ear shuts out, is seldom seen to be at all effected before the latter end of 

 July, or to be materially injured till a week or two in August, and then confined 

 to the greenest xvbeat, containg more sap, without extending to riper, containing 

 less, in the same field. 



That plants are liable to receive injury by frost in proportion to the quantity of 

 sap contained in them, or aqueous particles resting on them, is also generally 

 admitted; but by way of illustration to those who may not have given the subject 

 a consideration, I would wish to bring their recollection to what might have come 

 within their own observation, viz. that the early garden beans and peas planted in 

 October, and November, which have resisted the severe frosts in December, and 

 January, have, after a few warm genial days in April and May, that have quickened 

 vegetation and increased the quantity of sap, received a severe check by a much 

 slighter frost than they withstood in the winter months. To instance another 

 circumstance within my own knowledge — upwards of twenty years ago, two rows 

 of French beans had been planted in a border under a wall covered with long pro- 

 jecting thatch ; it happened by mere accident that one of them was planted within 

 side of the dropping of the eves, and the other without side ; and I well remember, 

 that in an evening the latter end of May a small misty rain fell, which was suc- 

 ceded by a frost in the night, and that so severe as to occasion a general remark 

 of being unusual at that period. The effect it produced on these beans was; that 

 every plant without side the dropping of the eves, exposed to the rain, was intirely 

 cut off ; whereas those withinside received but a slight check, and produced a crop, 

 having been piotected from the rain by the projecting thatch. 



How frequently has it liappened in the months of April and May, that a frost 



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