No. 6. Professor Moi-reri's Letter on the Potatoe Malady. 



191 



the evil, you perceive that it is by tiie rind 

 that the stalk is attacked. The morbid agent 

 carries its action from the rind on to the epi- 

 dermis, and though tliis last does not always 

 disclose mushrooms, it is not the less for that 

 struck with death. 



" The infection soon descends into the tu- 

 bercle itself. If the disease follows its 

 course, the tubercle mortifies forthwith. A 

 potatoe is not a root, but a real branch ; 

 whence it follows that a tubercle contains a 

 marrow, which is the eatable part to be pre- 

 ferred, and a separate rind ; between the 

 Hiarrow and the rind there is a zone of ves- 

 sels which represent wood. This construc- 

 tion is apparent to any one who chooses to 

 cut a thin slice of potatoe and place it be- 

 tween his eye and the daylight. The infec- 

 tion attacks that part which receives the sap 

 on its descent. 



" By following the progress of the evil 

 upon a great number of tainted tubercles, I 

 have been able to see how the evil, by one 

 continuous progress, at length reaches the 

 heart itself of the potatoe, and corrupts the 

 vegetable entirely. The skin of the dis- 

 eased potatoe comes off easily; the flesh no 

 longer cracks under the knife; a flatulent 

 liquid drips from the potatoe; a musty, and 

 presently an animal smell, analogous to the 

 smell of mushrooms recently cut, manifests 

 itself, and occasions considerable nausea. 



"The evil being traced to its source, the 

 cultivator must direct all his attention to the 

 destruction of the fungus, or mushroom, for 

 it is unfortunately but too true that all the 

 parasites of this genus, once introduced into 

 a country, remain there and propagate. This 

 year the epidemic has been geneial; the 

 germ exists everywhere; millions upon mil- 

 lions of propagules, if their numbers are 

 not diminished this year, will, next year, be 

 attacking the plants, and then it vi'ill be 

 more difficult to eradicate the scourge. 



"It is essential to adopt. the following pre- 

 cautions: 



" When the leaves are decidedly spoilt, 

 cut down the vines forthwith and burn them 

 on the spot, instead of taking them away. 



"When certain varieties or certain locali- 

 ties are free from the scourge at the time of 

 the harvest, it is always prudent to burn the 

 leaves, for a field may appear secure from 

 the botrydis when it is not so; several leaves 

 are attacked ; these leaves throw the propa- 

 gules on to the tubercles, which, if preserved 

 for purposes of reproduction, will spread the 

 plague the following year. 



" If the tubercles — potatoes — themselves 

 are attacked, it is essential to separate, as 

 speedily as may be, the tubercles that are 

 tainted from those that are not. Turn the 



sound ones to account as soon as possible, for 

 they are not noxious so long as the rind doe.^ 

 not become yellow. The diseased ones should 

 be burnt. 



" As it is probable that the tubercles pre- 

 served for seed will be infected with the 

 spawn of the mushroom, it would be advis- 

 able for cultivators who can, to procure tu- 

 bercles for reproduction from places where 

 the present scourge is unknown. 



"In case of using for reproduction the 

 tubercles of crops visited by the plague this 

 year, it will be necessary to submit them, 

 previous to planting, to the agency of lime, 

 as is practiced with wheat, and all plants 

 that are liable to invasion by parasitical bo- 

 dies. The process ought to be by the im- 

 mersion of the tubercles in lime water. 

 Twenty-five kilogrammes — 50 lbs. — of lime, 

 a quarter of a pound of sulphate of copper, 

 and three kilogrammes — six pounds — of ma- 

 rine salt, for twenty-five litres — quarts — of 

 water, constitute a preparation, the utility 

 of which, in the destruction of parasite ve- 

 getation, has been experienced by a great 

 number of well-informed cultivators. 



" In the plantations of the spring of 1846, 

 it is essential to plant potatoes in fields as 

 far as possible removed from those actually 

 infected this year, to avoid the danger from 

 the retention in the soil of the spawn of the 

 fungus. 



"The use of lime and of marine salt, 

 with a slight mixture of sulphate of copper, 

 is, as I have already said, of acknowledged 

 efficacy in the destruction of parasite germs. 

 Consequently, to powder over with such a 

 mixture, a soil in which diseased potatoes 

 have grown, is a good operation for destroy- 

 ing in that land the germs of the scourge. 

 The operation ought to be strongly recom- 

 mended everywhere. 



" The storing of potatoes from fields that 

 have been this year attacked by the scourge, 

 in cellars, caves, &c., will certainly be to 

 deposite the spawn of the mushroom in th.ose 

 very places. They should, therefore, before 

 receiving the potatoes, be thoroughly cleaned 

 and scoured with lime; and lime or ground 

 charcoal scattered over the bottom, — and on 

 the potatoes as they are stored — will con- 

 clude the series of operations, the most ra- 

 tional and the most certain for destroying, 

 ij" possible, the evil at its root. 



"C. H. MORREN, 

 " Member of the Royal Academy rf Sciences, <Jc. 

 " Liege, August 14th, 1845." 



Roses. — There are three modes, says 

 Buist, within the reach of all for the propa- 

 gation of garden or June roses — namely, by 

 layering, budding and grafting. 



