CULTURE OF THE GRAPE. 227 



out of the stomata, gradually spreading over the surface, 

 and drying in the form of a thin pellucid pellicle, scarcely 

 distinguishable by the naked eye. Upon or under this 

 pellicle, after some days, the vegetation of the fungus was 

 distinctly observable in the form of fine threads, ramify- 

 ing in all directions exactly as mushroom-spawn runs 

 through a 'brick.' A low magnifying power of two or 

 three hundred shows the object beautifully in the form of 

 most delicate lace-work. Fine particles of dust frequent- 

 ly adhere so thickly on the viscid surface as to interfere 

 with a good riew of the object. In a few hours, under 

 favorable conditions, little globular bodies may be ob- 

 served, forming all over the net-work of fibres. These 

 burst through the thin layer of extravasated sap, ' coming 

 up' very much like a fine crop of mushrooms. On twirl- 

 ing an affected leaf in a tumbler of warm water, the gum- 

 my matter dissolved, and carried with it the fungi, root 

 and branch. The conclusions deduced from these facts 

 seem to be that mildew is not a parasite in the proper 

 sense of the word, but rather a scavenger, decomposing 

 and changing into another form the excrementitious mat- 

 ter, or whatever it may be, thrown off by the leaves. 

 Mildew cannot exist upon a healthy vegetable surface; 



