i65 

 Aerial Potato Tubers. 



When tubers are not planted deeply, nor hilled up, the plant remains 

 green, while the root is liable to be greatly injured by drought or animals. 

 If subsequent rains cause the weakened roots to function sufficiently to keep 

 the aerial axes alive, small, colored tubers are developed on them from the 

 lateral eyes. This process is possible also under different conditions, yet 

 the root must be diseased and able to convey only very small amounts of 

 water from the soil to the leafy stems. If cuttings are taken from the older 

 parts of the stem, they can be forced to form tubers in the leaf axils. 



Premature Ripening of Fruits. 



In years of continued drought, as, for example, 1904, complaints be- 

 come most numerous that fruit does not keep. Summer fruit indeed ripens 

 more quickly and can be brought to market one to two weeks earlier, but the 

 flavor leaves much to be desired. A\'inter fruit remains smaller, as a rule, 

 is less juicy and w^ell-flavored and decays more quickly, or it needs a much 

 longer time in storage in order to become fit to sell. The former may be 

 observed with light soils, the latter has often been found^ when, with heavy 

 soil, rains occur after a period of drought, causing a further growth of the 

 fruit which, until then, had been retarded by a scarcity of water. 



The condition here pictured is explained in the discussion of the fact 

 that the quality and keeping qualities of the fruit depend upon two factors. 

 First of all, each fruit must have sufficient time for the penetration of the 

 water and food substances necessary for its maturity; this takes place at 

 the time of swelling. Then the oxidation processes of ripening set in grad- 

 ually, in which the reserve material, stored in the form of starch, is used up 

 in respiration. The longer time the fruit has to store up the material sup- 

 plied by the leaves, the better provided it is for the process of ripening and 

 the better are the keeping qualities. If this process is interrupted ahead of 

 time by drought, the processes of ripening, the conversion of starch into 

 sugar, find comparatively little material present. In normal summer 

 weather, i. e., alternate sunshine and rain, the fruit during the process of 

 ripening also takes up mineral elements besides water, as Pfeiffer and I have 

 proved. An absolute increase in mineral substances takes place shortly 

 before complete ripening. This naturally appears relatively small in com- 

 parison v'ith the greater increase in organic substances. With a continued 

 scarcity of water this increase does not take place and the fruits quickly 

 use up the scanty materials. The acid store is scanty, the formation of 

 sugar still less, which accounts for the insipid taste and the poor keeping 

 qualities. 



In winter fruit, processes of ripening are completed only in storage. 

 But in all other respects the same point of view holds good. If the weather 

 during the summer is favorable for the absorbing of large amounts of re- 



1 Monatsschrift fiir Pomologie unci praktischen Obstbau von Oberdieck unci 

 Lukas, 1863, p. 272. 



