TREATMENT OF TUBERS, &c., FOR PLANTING. 41 



It has been noticed also that those potatoes which grow 

 nearest to the surface, especially such as have been par- 

 tially exposed, and have obtained a greenish brown ap- 

 pearance on the skin, always produce the healthiest and 

 best plants. Acting upon this observation, it is a practice, 

 especially with gardeners, to expose the tubers intended 

 for planting to the action of the sun and the air for some 

 time, in order to produce the same eifect on the potato, 

 as when it was attached to its parent stem, was seen to be 

 of advantage to its reproductive powers. This practice can 

 hardly be carried out on a large scale for field purposes ; a 

 week or two's exposure, however, on the ground, at the time 

 of lifting the crop, in the manner described at p. 436, vol. i., 

 would no doubt be of great advantage, by reducing the 

 chances of injury they sustain in the heap, and thus keep 

 them in a better condition for sowing in the spring. 



A difference also has been observed in the germinating 

 powers of "sets" cut from different parts of the tuber ; that 

 those taken from the "rose end," or upper part (see wood- 

 cut), produce more vigorous plants, and ripen earlier than 

 those taken either from the centre or from the opposite extre- 

 mity, or "heel," as it is commonly termed. These points, 

 which have some practical importance, are quite consistent 

 with the chemical constitution of the potato, 1 and help to 

 strengthen the claims which science has upon all engaged 



1 Dr. Fromberg's investigations tended to show that the part from which 

 the shoots are most abundantly produced contains more moisture than the 

 opposite end, and that the proportion of inorganic matter also is greatest in 

 the rose end, and continues so during the successive periods of growth. The 

 following data bearing upon and confirming these points, are extracted from 

 the results of his numerous analyses: 



