144 THE GRAPE. 



ing them useless ; the leaves also will fall off after a short 

 time, and the whole plant become seriously injured. 

 These white patches are the fructification of the parasite ; 

 when viewed under the microscope, there is exhibited a 

 multitudinous congregation of little mushroom-looking sub- 

 stances, and if suddenly jerked, the tiny sporules may be 

 seen detached, and floating in the atmosphere, so minute 

 and subtle, and in such countless numbers, that it is not 

 unreasonable to suppose (beside the immediate develop- 

 ment and rapid vegetation of thousands of them under 

 favorable influences) many are absorbed by the stomata or 

 breathing pores on the under surface of the leaves, and 

 conveyed into the interior, simply by the descending 

 movement of the elaborated sap, which is afterwards con- 

 verted into woody-fibre, and in its turn becomes the 

 organized medium by which the ascending sap, in the fol- 

 lowing spring, flows with greater velocity to the unfolding 

 leaves. The secreted sporules may then be re-conducted 

 upwards, and conveyed onwards to the foilage, and there 

 remain dormant, until the favorable circumstances occur 

 for their germination, when they spring into renewed life, 

 and speedily produce another crop of seeds for a future 

 generation. This kind of mildew seldom does any mis- 

 chief after the growth approaches towards ripeness, or the 

 fruit is in the last swell, and as it generally begins to 

 appear about the early part of July, during damp and 

 close weather, those plants which have been more or less 

 forwarded by artificial heat are almost free from its attacks ; 

 but in the Cold Grapery or Retarding House we should be 

 on our guard, and when storms or damp weather occurs, 

 strew sulphur on the floor of the house, in the proportion 

 of one pound t6 each fifteen or twenty square-yards, and 

 withhold water for the time being, keeping the house quite 

 close, if cloudy, and allowing the temperature to rise some- 



