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'OL. XXIV. Second Series. ROCHESTER, N. Y., MAY, 1863. 



No. 5. 



' THE TfiUE CAUSE OF THE POTATO DISEASE." 



We have long been satisfied that the potato 

 isease is caused by a fungus. In fact, we think it 

 ill soon be proved that nine-tenths of all the 

 aladies which afi'ect trees, plants, grains, vegeta- 

 es, &c., are caused by some of the numerous 

 rms of fungus, either taken up by the roots, as is 

 16 case with smut in wheat and the pear-tree 

 ight, or by growing on the leaves of the plant, 

 ce mildew on the grape, turnip, &c. 

 Many people appear to think that fungus is a 

 ■ontaneous production ; but such is not the case. 

 is produced from seed, or is propagated from the 

 ant itself. There is no mystery about it, except 



far as all vegetable growth is a mystery. The 

 eds are generally invisible to the naked eye, 

 It they are none the less real, and it should be 

 ir aim to destroy them quite as much as to de- 

 -oy the seeds of thistles and other noxious 

 aeds. If this is not done our useffll plants and 

 getables will soon be over-run with these injuri- 

 s parasitic plants. Smut in wheat is caused by a 

 Qgus attached to the seed, and this is effectually 

 stroyed by " pickling " the seed wheat in cham- 

 r lye. Were it not for this practice, our wheat 

 )uld soon be injured to an immense extent, 

 hat has been done in the case of wheat can be 

 ne in the case of other plants liable to the at- 

 ;ks of fungus when more is known in regard to 

 s subject. But to return to the potato disease. 



the Genesee Farmer for December, 1861, page 

 3, we published the following article: 



"the potato disease. 

 'There can no longer be any doubt that this 

 ■■tructive malady is caused by a fungus. 

 'In the case of the grai)e-vi"ne mildew the fun- 

 1 merely creeps over the surface, and sulphur 

 1 destroy it. But unfortunately the potato fun- 



penetrates into the tissues of the plant, and all 



remedies which have been suggested, such as 

 loving the portions when diseased, drying the 

 ers, &c., must be considered jis palliatives rather 

 a preventives. 



"The rapidity with which the disease spreads 

 itself is shown in a recent German work On the 

 Cause and Treatment of the Potato Disease, by 

 Dr. De Bary.* It is calculated that one square 

 line of the under surface of the leaves is capable 

 of producing 3,270 spores, and as each of them 

 yields at least six zoospores (the number being 

 sometimes as high as 16,) we have 19,620 reproduc- 

 tive bodies from that small space. The quantity 

 therefore, yielded by a single plant is enormousi 

 and as the mycelium from the zoospores is capable 

 of penetrating the cellular tissue in twelve hours, 

 and when it is once established there and bursts 

 through the breathing orifices or stomates of the 

 leaves, it perfects it fruit in from fifteen to eighteen 

 hours, and since the zoospores are perfected and 

 ready to germinate in twenty-four hours from their 

 being placed in water, it is scarcely possible to cal- 

 culate the myriads of plants that may spread from 

 a single center. As continued moisture is abso- 

 lutely necessary for the germination of the spores 

 and the production of the zoospores, it will at once 

 be understood how rapidly the disease is propagated 

 in wet weather, especially if it be warm, and what 

 a check to the disease a dry season must be. It 

 will also be apparent under what circumstances the 

 zoospores will have readiest access to the tubers, 

 and that those which are nearest the surface have 

 a less chance of escaping than those which pene- 

 trate deeper into the soil. 



" He shows that the disease is .propagated from 

 the tubers, and suggests that a spot of ground be 

 specially selected for raising seed potatoes, where 

 all the most likely means can be used to keep off 

 the fungus, such as the instant removal of diseased 

 leaves, and, if necessary, the removal of the stems, 

 so that the zoospores can not be washed down to 

 the tubers. A repetition of the process for a few 

 years might banish the disease from the farm. A 

 second hilling-up to cover the tubers more efl'eetu- 

 ally, and to throw off the water containing the 

 fungus spores, is also recommended." 



Prof. S. W. Johnson, of Yale College, in a re- 

 cent number of the Country Gentleman, pro- 

 nounces this ^'■the true cause of the' potato disease,''^ 

 and furnishes some additional facts in regard to the 

 experiments of De Bart, Kuhn, and other Ger- 

 man botanists. He says : 



* Die gegenwartiff herrschende Kartoffelkrankheit, ihre Ur- 

 sache, und ihre Verhutung. Von Dr. A. De Bary, I'roft^sor der 

 Botamk zu Preiburg. Leipzig, 8vo., pp. 76, 1 tab. lith. 1S61. 



