388 



Degeneration in Potatoes. 



[OCT., 



necessary for the work. For the same reason many tubers 

 remain almost unchanged as to starch contents when the crop 

 is lifted in the autumn. These are illustrations of somewhat 

 extreme cases, but the fact that potatoes in general remain 

 " floury " for a longer period of time than formerly, indicates 

 a gradual and general loss of power on the part of potatoes to 

 produce the necessary quantity of diastase. 



A total absence of diastase was proved in the case of tubers 

 that had failed to sprout. In other examples the relative 

 amount of diastase present was ascertained to be in proportion 

 to the number of sprouts formed. 



Diastase is first formed, and in greatest abundance, at the 

 apical or free end of a tuber, and for this reason the earliest 

 and most vigorous sprouts are produced in this region in a 

 normal tuber. When the presence of diastase is on the wane 

 it also lingers longest in the apical region ; hence, in a large 

 percentage of deteriorating tubers, sprouts from a single apical 

 " eye " are alone produced, as in Fig. i ; and in many instances, 

 where the supply of food is very scanty owing to the absence 

 of diastase, these sprouts perish at a very early age, as shown 

 in Fig. 2. In Fig. 3, which illustrates the grower's ideal even 

 surface — a factor of undoubted value when the loss resulting 

 from paring is the object in view — the power of growing or 

 sprouting has been completely lost, owing to deterioration of the 

 fibro-vascular system and the comparative absence of diastase. 



During the past three years a series of experiments have 

 been conducted with the object of imparting new vigour to 

 potatoes intended for " seed." It must be admitted that the 

 results obtained up to the present have not been very encourag- 

 ing, the time being too short to remove the deterioration 

 which it has taken a prolonged period of more or less intensive 

 cultivation to establish ; nevertheless certain points have been 

 noted which may prove to be of value to future experimenters. 



Degeneration appears to be mainly due to the vegetative 

 method of reproduction commonly followed. Even in the case of 

 seedlings, the parents of these must at least be closely related. 



The nearest approach to a return to normal conditions is in 

 the case of potatoes that have been grown for three years in 

 succession on the same patch of sandy ground and without a 

 trace of manure of any kind. The original "sets " of a highly 



