274 



Wisconsin State Hokticultubal Society. 



Hum or spawn quickly descends within the stalk and enters the 

 tuber. Fig, 1 represents a section of a potato showing its vascu- 

 lar bundles, air-passages and starch-cell structure. In the case of 

 the potato-rot the decomposition first starts in the vicinity of these 

 air-passages, ultimately destroying all the nitrogenous matter 

 which covers and holds together the entire cell-structure. These 

 vascular bundles form a perfect zone over the entire potato, 

 branching at points to the surface, where they terminate and form 

 the bud or so-called eye of the potato. 



Fig. 2 represents a section illustrative of this fact, g^ a, and t, 

 are the air-passages as above described. When a potato is 

 broken down by fermentation it is resolved into a soft, pulpy 

 mass, a condition to which all potatoes are reduced when subject 

 to any kind of fermentation or rot, consisting principally of starch- 

 bladders or cells, c and h — 5,5 are broken cells — p, starch- 

 granules. 



Fig. 3. Starch Cell. 



Fig 3 represents a single starch cell, d, as seen on viewing a sec- 

 tion of a sound potato, and which is composed wholly of cellu- 

 lose,' but is held in position by the nitrogenous and cellulose 

 substances, a and h. 



When a sound potato is grated down the cell-structure and at- 

 tachments are broken up because of their perfect cohesion to one 

 another. One cell cannot be broken without destroying all its at- 



