356 BULLETIN OF THE BUSSEY INSTITUTION. 
general tirade against the folly of planting potatoes after any of the 
above-mentioned crops.* There is as yet no sufficient reason for not 
following them by potatoes if one wishes to, other than that the stub- 
ble of some of these, crops may make the land more moist than 
that of others. Potatoes grown upon a soil where grass or clover 
have previously been ploughed in may suffer from rot, simply because 
the sods keep the land moist. It is quite probable that the odspores 
of Peronospora infestans will be found concealed in some common 
plant eaten by cattle, and as it is well known that the spores, particularly 
the odspores, of many fungi, are so tough that they pass through the 
alimentary canal of animals without losing the power of germination, 
it is evident that the chances of avoiding the rot are greater if one 
makes use of some of the mineral manures in place of animal man- 
ure. The fact that certain crops are manured with animal manure, 
while others are not, may be sufficient to account for the prevalence 
of the rot when potatoes follow such crops. 
It is, of course, of the first importance to avoid planting tubers which 
are already rotten, but that no sensible farmer would think of doing. 
How to recognize small amounts of mycelium in nearly sound pota- 
toes does not admit of any practical solution. The botanist who has 
studied the subject can do it by microscopic examination, but the 
farmer has neither a microscope nor sufficient knowledge of micro- 
scopic manipulation, and, practically, it would not pay to send cer- 
tain tubers, as samples of a large quantity, to a botanist, to decide on 
the probable amount of mycelium in the whole. Judging from the 
results obtained in England, it makes no difference whether the tubers 
are planted whole or sliced, as far as liability to the disease is con- 
cerned. Theoretically, it would appear to be an advantage to plant 
* During the last few months, notices have appeared in the Agricultural 
Reports published at Washington, and in several agricultural journals in dif- 
ferent parts of the country, to the effect that, in consequence of the discoveries 
of Professor De Bary, it is now known that the potato-rot is propagated by - 
means of the odspores of Peronospora infestans which hibernate in clover and 
other fodder-plants; and farmers are warned against planting potatoes after 
these crops. In justice to Professor De Bary, the public should be informed 
that he has never said any thing which could, in the least, warrant the state- 
ments above mentioned. Without saying any thing more about the question 
whether the rot is really more common after any particular crop, or not, it is 
unfair to represent Professor De Pary as authority for the sweeping state- 
ments of some of our agricultural journals. 
