32 



BOAED OF AGRICULTURE. [Pub. Doc. 



The Development of the Potato Tuber. — While Sitar Potatoes, 2)lanted 

 May 20, at Burli7igton, Vt. ( Yields and Sizes of Tubers at Differ- 

 ent Dates.) 



It is evident at a glance, therefore, that more than one- 

 half of the marketa))le crop was developed after the third 

 week of August, and the results of similar trials two other 

 years bear out this general conclusion. 



Here, then, we have the standard by which we may meas- 

 ure the relation of the diseases of the potato to its devel- 

 opment ; for it is at this critical period and immediately 

 subsequent to it — in other words, in the early stages of this 

 possible formation — that the most destructive potato mal- 

 adies occur. As said, these plants were properly sprayed to 

 give full protection against insects and blights of all kinds ; 

 moreover, they were kept free from weeds. It is only as 

 perfect root and leaf activity is thus made possible that such 

 full development can occur. This will become the more evi- 

 dent as we inquire into the conditions necessary for nutrition 

 and growth of the plant. 



The potato tuber carries about 79 per cent of water, 17 

 per cent of starch, and 1 per cent of mineral matter. It 

 is evident, therefore, that the chief requirements for the 

 nutrition of the plant during the period of tuber forma- 

 tion are not commercial or other fertilizers to supply the 

 mineral matter, although the}^ are in their minor wav im- 

 portant, but adequate ^irovisions for furnishing the Avater 



