442 Journal of Agriculture , Victoria. [lo July, 1911. 



ABNORMAL GROWTHS OF THE POTATO. 



D. McAl-piiie, Vegetable Patliologist. 



In the comparatively dry summer of 1909-10, at the Burnley Horti- 

 cultural Gardens, some of tlie \ otatoes grown were rather small ; others- 

 produced an over-growth of secondary tubers, as in Figs, i and 3, and 

 the so-called " wet-ends " were not infrequent. All the.se gradations 

 from the non-formation of tubers to their excessive development may be 

 explained by the varying nature of the growth. 



The normal growth of the potato consists in one or more of the 

 " eyes " or buds growing out at the expense of the nourishment stored 

 up in the tuber. By the time this is exhausted, leaves and roots are 

 usually formed, and an independent supply of food is obtained wherebv 



I. SUPERTUBERATION PRIMARY, SECONDARY, AND TERTIARY TUBERS. 



2. SUPERTUBERATION SECTION. 



new tubers are produced. If, however, the weather conditions are favour- 

 able in the early stages of the plant's growth, so that there is a profuse- 

 development above ground, and a dry spell supervenes at the time the 

 tubers should be forming, then the stoppage in the flow of sap may pre- 

 vent their formation altogether. Hence it is that either no tubers, or 

 only small ones, may be produced by a plant which has luxuriant foliage. 

 But the tubers formed in the usual way, and, while still attached to^ 

 the parent stem, may continue their growth in various ways, and this may 

 give rise to the different appearances known as " second growth " or 

 sprouting, super-tuberation, and wet ends (Fig. i, at bottom). The 

 drier the summer, the more quickly the tubers ripen, and this causes en- 

 largement and multiplication of the cells. The cell walls, with the- 

 exception of the very youngest at the eyes, lose their capacity for stretching.. 



