112 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



vine, showed itself in 1819, exactly forty years ago : " Rains had 

 fallen but sparingly in the autumn and during the first winter 

 months, when, from the 21st of July of that year, heavy and re- 

 peated rains drenched the ground, and made all springs to over- 

 flow; these rains lasting, at intervals, till late in the year. On 

 the 13th of December, he observed the first symptoms of rust, 

 which, during a whole month, spread among his vines, and caused 

 great damage to the muscadel and hanepoot grapes, afiecting the 

 Steendruif in a slighter degree." 



I have since visited most of the vineyards at Hottentot's Hol- 

 land, where the blight has injured the vines to a fearful extent, 

 by annihilating great portions of the crops. At some farms, all 

 sorts have been smitten, but the muscadel and hanepoot nearly 

 everywhere ; the only place which has been spared hitherto being 

 that of Mr. H. Theunissen's, whose vines grow on a slope, and 

 have gravel for their soil. 



I am very sorry, however, to have to report that amongst the* 

 lacrima christi grapes, on Mr. P. Myburg's estate, I met with the 

 true vine-mildew, which had been observed there but a few days 

 previous to my arrival, upon a few individual shrubs. The 

 very existence (however limited) of a disease, which is known to 

 spread, at times, with fatal velocity, deserves the utmost vigi- 

 lance and attention ; and the following remarks are results of 

 my microscopical investigations on this important subject : 



To the naked eye, the vine-mildew (Oidium Tuckeri), presents 

 itself in a form of a byssaceous mould, which covers the stalks, 

 leaves, and grapes, with a white powdery substance, and imparts 

 a disagreeable musty odor to the parts. It is particularly visi- 

 ble on the pedicels, and upon the surface of the fruit ; less on 

 both sides of the leaves, and shoots. 



When examined under a microscope of high power, very minute 

 whitish-grey spots appear upon the cuticle. At first, these specke 

 are solitary, and scattered here and there over the surface, but 

 they soon become more or less united, and assume a cloudy 

 appearance. They then consist of a conglomeration of very 

 delicate articulated, white threads, which interlace each other, 

 and spread rapidly in all directions over the surface of the plant. 

 These threads constitute the spawn {mycelium), and from them 

 spring the fungi in the shape of minute, erect, fertile, club-shaped 

 filaments. The latter bodies, which are scarcely the eighth part 

 of a line high, are made up of a number of cells, separated by 



