I. AGRICULTURE AND RURAL ECONOMY. 397 



ing classes ; and a method of utilizing the diseased potatoes 

 has been made public at the instance of the British govern- 

 ment. This depends upon the fact that the starch of the 

 potato is not aflected by the disease, but retains its nutritive 

 properties. 



The process consists in rasping the peeled tubers, upon a 

 bread grater, into a tub of water. The starch sinks to the 

 bottom in a few minutes, and the diseased matter, woody- 

 fibre, etc., is suspended in the water, and should be poured 

 off with it. Fresh water is then to be added, the starch 

 stirred, and again allowed to settle. Two or three such 

 washings will thoroughly remove all impurities, and render 

 the starch fit for use. If dried, it can be kept any length of 

 time, and can be used, like arrow-root, for puddings and cakes, 

 or, mixed with flour, as bread. 22 A, An just 31, 1872, 202. 



THE POTATO DISEASE IN GREAT BEITAIN. 



A very interesting article upon the recent outburst of the 

 potato disease in Great Britain has been communicated by 

 Mr. L. G. Smith to the October number of Hardwicke's Science 

 Gossijy. In this the author refers to the fiict that it was not 

 until 1841 that the disease was brought prominently into 

 notice, although as far back as 1830 a disease of the potato 

 was known in Germany under the name of the dry rot. In 

 its more recent manifestations, it appears to have been ob- 

 served in Canada and the United States, but not before its 

 memorable outburst in Western Europe in 1845. 



The true cause of the evil is now well ascertained to con- 

 sist in the disorganization of the tissues of the plants, caused 

 by a fungus known as Peronospora infestavs. This never 

 develops itself on the upper surface of the leaf (which ap- 

 pears to be quite impervious to its attacks), and it seldom 

 originates in the stems; but the mycelial threads pass down 

 from the leaves, and soon reach the tuber. The stem and 

 leaves then rapidly rot and fall ofl" upon the earth, in an of- 

 fensive mass. So rapid, indeed, is the growth of the fungus, 

 that in a few days it will spread from plant to plant over a 

 large tract, giving to the field the appearance of having been 

 attacked by frost. The prime cause of the death of the leaf 

 is probably to be found in the choking of its breathing pores, 

 resembling in a measure the action of croup in the human 



