SECRETARY'S REPORT. 15 



of potatoes, each acre yielding about 300 bushels, or eight tons, must be able 

 to extract 1,2G5 pounds of potash, if he would produce a sound, rightly con- 

 stituted crop. Of this he may return in the tops 250 pounds, having removed 

 1,015 ; while the waste has not been repaired by using guano and sea-weeds 

 which contain none, and barn-yard manure, which possesses but a small pro- 

 portion. It is easy then to understand, if this scarce commodity is not annu- 

 ally supplied in some manner, an element will soon be withdrawn that is 

 essential to tho vitality of this vegetable. As the malady has generally pre- 

 vailed after the middle of July, it may be avoided by planting early varieties 

 that may mature, be harvested and consumed before it makes its appearance. 



It has been found by observation that potatoes planted in peaty, mossy or 

 virgin soils, or in recently cleared burnt lands, or in the valleys of granite 

 countries which had not been much subject to culture, were comparatively 

 exempt and furnished much healthy seed to the agriculturist, lor all these 

 abound in potash. It is also a remarkable coincidence that Asiatic cholera 

 rarely visited regions in which granite predominated. 



If, then, potato blight is mainly occasioned by a deficiency of this alkali, 

 we may hope to diminish or avert it by planting the potato on suitable lands 

 manured with ashes, muck, well composted vegetable substances which con- 

 tain potash. Even barn yard manure may be used with advantage, if it has 

 undergone the process of nitrification. This occurs whenever it is collected in 

 a heap, mixed with earth rich in vegetable material, and allowed to ferment 

 and decompose during summer, where the air can have free access to it. The 

 nitrogen of the atmosphere enters into new combinations with the fermenting 

 organic matter, nitric acid is produced, and then nitrate of potassa is formed. 

 In a similar way the nitre of commerce, so valuable for manufacturing impor- 

 tant compounds, crystalizes rapidly and abundantly in beds on tho surface of 

 the ground in hot climates. One great advantage of drainage is, that it ren- 

 ders the soil more permeable to air, and facilitates the production of these 

 valuable nitrates which readily dissolve and are immediately appropriated by 

 the growing crops. 



Another disease which formerly prevailed extensively, particularly in Eu- 

 rope, is called the potato curl. It is propagated by contagion, in consequence 

 of which the plants become rapidly and successively curled and the tubers 

 shrivel. It i<j attributed to a preternatural thickened condition of the juices 

 in the tuber planted. The sap is in such a state that it cannot circulate 

 freely in the growing foliage. Since greater care has been used in procuring 

 uninfected potatoes for seed, and preserving them unchanged during the 

 winter, it has almost disappeared. 



One mere epidemic, which has devastated the vineyards of Europe, and may 

 extend to this country, deserves a brief notice. It is the vine disease in which 

 brown spots first appear on the leaves and permeate quite through their tissue, 

 then small white patches of a soft and delicate fungus seize the under side of 

 the leaves, causing rapid defoliation, extend to the fruit stalks, attack the 

 berries, choke up their pores, mechanically confine them with their dense 

 felty substance, arrest their growth, and severely injure the whole vine. These 

 white patches are produced by a species of parasite called Oidium. They are 

 the growth of fungoid vegetation, the plants of which analagous to seeds are 

 so extremely small that they are invisible to the naked eye, and can float in 

 the air scarcely influenced by the force of gravitation, each one capable of 

 producing millions of its kind. When viewed under the microscope, they ap- 

 pear like a vast congregation of little mushroons. This kind of mildew seldom 

 does much mischiet when it commences after the fruit begins to ripen. Nor 

 is it apt to attack perfectly healthy vines, but chiefly those whose vital energy 

 has been long impaired by various debilitating causes. Excessive changes 

 of temperature, damp and close weather favor its develofment. The grape 

 vine is a gross feeder. It requires, with other nutriment, potash in various 

 combinations, as silicate, nitrate, tartrate, soap sudd, &c.; ammonia, or nitro- 



