Potato Culture. 



rable by its giving birth to a disease 

 which threatened the entire destruc- 

 tion of the potato crop, and which 

 caused suffering and pecuniary ruin 

 to an incredible extent throughout 

 Europe. 



The potato, at the time of the ap- 

 pearance of the potato disease, was 

 almost the sole dependence of the 

 common people of Ireland for food. 

 That over-populated country expe- 

 rienced more actual suffering in con- 

 sequence of the potato disease than 

 has any other from the same cause. 

 Although this di ease has never, in 

 this country, prevailed to the same 

 ruinous extent that it has in some 

 others, yet we are yearly reminded 

 of its existence, and in some seasons 

 and localities its destructive effects are 

 seriously apparent. 



The final or culminating cause of 

 the disease known as the "potato- 

 rot" is Botrytis (peronospora) infes- 

 tans. This may be induced by many 

 and various predisposing causes, such 

 as feebleness of constitution of the 

 variety planted, rendering them an 

 easy prey to the disease ; by planting 

 on low, moist land, or on land high- 

 ly enriched by nitrogenous manures, 

 causing a morbid growth which in- 

 vites the disease; also by insects or 

 their larvae puncturing or eating off 

 the leaves or vines. But by far the 

 most wide-spread and most common 

 cause of the disease is sudden changes 

 of atmospheric temperature, particu- 

 larly when accompanied by rain. 

 Drought, though quite protracted and 

 severe, unless accompanied by strong 

 drying winds, and followed by sudden 

 and great reduction of temperature, sel- 

 dom affects the potato seriously. It is 

 not uncommon in the Northern States, 

 during the months of August and 

 September, for strong westerly winds 

 to prevail for many days in succession. 

 These winds, coming from the great 

 American desert, are almost wholly 



devoid of moisture, and their aridity 

 is often such that vegetation withers 

 before them as at the touch of fire. 

 Evaporation is increased in a pro- 

 digiously rapid ratio with the velocity 

 of wind. The effects of the excessive 

 exhalation from the leaves of plants 

 exposed to the sweep of such drying 

 winds' are at once seriously apparent. 



When these winds finally cease, the 

 atmosphere has a low relative humi- 

 dity, not enough moisture remains in 

 the air to prevent radiation ; the heat 

 absorbed by the earth through the 

 day is, during the bright, cloudless 

 night, rapidly radiated and lost in 

 space, and a reduction in temperature 

 of twenty to thirty degrees is the con- 

 sequence. 



In the first place, the potato-vines 

 suffer by excessive exhalation ; in 

 the second, by sudden reduction of 

 temperature, and, though not frozen, 

 their functions are much deranged, 

 and their vitality greatly enfeebled 

 To use a common expression, the 

 plant " has caught a violent cold that 

 has settled on the lungs." 



The leaves (which are the lungs of 

 plants) now fail to perform their func- 

 tions properly. The points of many 

 of the leaves turn brown, curl up, and 

 die. 



The ascending sap, not being ful- 

 ly elaborated by the diseased leaves, 

 oozes out through the skin of the stalk 

 in a thick, viscous state, and the plant 

 to all appearance is in a state of con- 

 sumption. 



At this stage the ever-present mi- 

 nute spores of the Botrytis infestans 

 eagerly pounce on the sickly plant, 

 fastening themselves on its most dis- 

 eased parts. The Botrytis infestans 

 is a cryptogamous plant, and is in- 

 cluded in the Mucidineous family, 

 (moulds.) It is a vegetable parasite 

 preying upon the living potato plant, 

 like lice or other animal parasites upon 

 the animal species. 



