On the Prevention of Curl and Dry -Rot in Potatoes. 169 
necessary to state briefly the doctrine propounded by the most 
eminent vegetable physiologists of the j)resent day, who affirm 
that during the act of commencing germination a substance called 
" diastase " is generated from the nitrogenous substances contained 
in the germinating seed, which diastase assists in the conversion of 
starch into the gum, sugar, &c., which are required for the 
nourishment of the young shoot. The potato contains a very 
small per centage of nitrogenous matter. I would, therefore, 
venture the suggestion that the great addition made in the process 
of ripening to the already large stock of starch contained in the 
tuber may be more than can be converted into gum, sugar, &c., 
by the small quantity of diastase generated in the germinating 
potato. If this be the case, then it would follow that the diastase 
being mixed with too large a proportion of starch (like leaven 
mixed with too large a proportion of dough) only does its work 
imperfectly, and the result is a weakly shoot, whilst a portion of 
the starch, failing to receive the vitalizing influence of the diastase, 
undergoes the natural course of decay, and produces the symptoms 
peculiar to dry-rot, wet-rot, or curl. This sup])osition is, of 
course, pure theory, and must not be confounded with the facts 
on which it is based. To make it quite clear where the one ends 
and the other begins, I will very briefly recapitulate. Facts have 
been brought forward to prove that ripe sets are subject to curl, 
and vice versa, also that a large addition is made to the quantity of 
starch in the potato in the process of ripening. Direct experi- 
ment also j)roves that " diastase ' is required for the germination 
of seeds, which diastase can only be formed from some substance 
containing nitrogen : potatoes contain a very small proportion of 
such substances, and therefore can have but very little diastase. 
Here our facts end, but from these premises I would hazard the 
deduction that if we allow our seed potatoes to ripen they acquire 
more starch than can be made available to the growing shoot ; 
which excess naturally decays, and then infects and injures, or 
even destroys, the plant with which it is connected. A similar 
effect is produced in the human subject when more food is taken 
into the stomach than the gastric juice is able properly to digest. 
The imperfectly converted aliment produces inconvenience of 
various kinds, and, if persevered in, derangement of the whole 
system, though the food itself in moderation may be perfectly 
wholesome. 
It would be doing injustice to the theory above stated, if it 
were sent forth to the public withcmt a brief notice of some of 
the objections which will at once occur to those conversant with 
the subject. The first that I shall allude to is that the manage- 
ment of seed potatoes during winter, the mode of planting, and 
mure especially the nature of the season after planting, exercise a 
