
50 
leaves, while still living and active, from which the passages of 
transference at the nodes of the stem have been cut off by the fungus; 
just as the eventual withering of the leaves is due to the blocking of 
their water conduits when all the vessels are stopped up. 
At the same time, the attempts I have made to induce the form- 
ation of these crystalloids artificially have failed so far. 
Neither ringing, nor ringing combined with destruction of the pith 
with a hot skewer—to destroy the internal phloém—has given satis- 
factory results as yet, though the leaves of healthy plants withstand 
this drastic procedure much better than might be supposed. 
Here again I must reserve further particulars for the fuller paper. 
In conclusion, it is evident that the efforts of the potato-grower 
must be directed to the selection of sound sets, and to the careful 
preparation of his ground. I hope to show later that it is a fatal pro- 
cedure, even with sound sprouts, to allow the young shoots to lie in 
contact with raw manures, as it is wid wounds and small rotting 
spots at and near the collar that new infections occur. The same 
arguments apply to wet soils and situations, and the disease is par- 
ticularly apt to increase when wet and cold weather supervenes on 
the early growths. 

