62 The Potatoe Plague. 
The infection soon descends into the tubercle itself. If 
the disease follows its course, the tubercle mortifies forthwith. 
A potatoe is not a root, but a branch, whence it follows that a 
tubercle contains a marrow, which is the eatable part to be 
preferred, and a separate rind; between the marrow and the 
rind there is a zone of vessels, which represent wood. This 
construction is apparent to any one who chooses to cut a thin 
slice of potatoe, and place it between his eye and the day 
light, ‘The infection 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 diseased potatoe comes off easily; the flesh 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 oceasions 
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 gen- 
eral; the germ exists every where: millions upon millions of 
propagules, if their numbers are not diminished this year, 
will next year attack the plants, and then it will be more 
difficult to eradicate the scourge. 
Ji is essential to adopt the following precaution : 
When the leaves are decidedly spoilt, eut down the vines 
forthwith, and burn them on the spot, instead of taking them 
away. 
When certain varieties or certain localities are free from 
the scourge at the time of the harvest, it is always prudent to 
