PRESENT DISEASE IN THE POTATOE. 29 



a part of a single leaflet, which may dry and become 

 dead. It may even commence at any portion of the leaflet 

 in the centre forming a little dry circle, which may be- 

 come a simple hole ; or it may commence on one side, or 

 round the edge of the leaflet. (Plate v., fig. 4.) 



(105.) In some cases the gangrene is propagated down 

 the leaf- stalk, thus cutting off nourishment from the other 

 leaflets, which then die from secondary causes, being thus 

 as completely isolated as if they had been removed from 

 the plant by the gardener's knife. 



(106.) From the leaf it may be propagated down the 

 stalk, and in this way cut off the supply from other entire 

 leaves, or even from whole stems, which, from their hav- 

 ing no nourishment, must perish. 



(107.) At other times the malady attacks the base of 

 the leaflets in the first instance, and thus cuts off* the leaf 

 from further nourishment. It may in the same way attack 

 any part of the stalk, and cause the death of the part above 

 it. 



(108.) Very frequently it is first found in the under- 

 ground stem of the plant, or those parts of the principal 

 stem which are situated below the earth's surface. In 

 this instance the supply of nourishment is entirely cut off 

 from the upper part of the plant ; and the top will fre- 

 quently die from this cause, as rapidly as if it had been 

 mown down with a scythe. 



(109.) It is from this cause that potatoe plants in a green 

 succulent state seem at certain times prematurely to wither 

 up in a few hours. The stems, separated from the root by 

 the action of the disease, are sometimes filled with water 

 by a little rain or heavy dew, which renders them fresh 

 and beautiful to the sight. They are sometimes exposed 



