323 



cells, free from chlorophyll, 3 to 4 times as long as they are broad, exist 

 between the cambium and the bark parenchyma which are not present in 

 the land specimens. This difference becomes greater, when the older parts 

 of the plant are compared with one another. Below the surface of the 

 water these cell rows become a thick, lacunar tissue Epidermis and bark 

 soon go to pieces here. The cells which form this special tissue are de- 

 veloped from the cambium. 



The sudden excess of water, which causes the rupturing of part of the 

 plant, destroys the equilibrium in the epidermis, or the cork layer present 

 instead of the epidermis, and in the fleshy parenchyma body. Especially 

 after previous periods of drought, the elements of the upper epidermis be- 

 come thicker walled and less elastic and are not able to accommodate them- 

 selves rapidly enough to the swelling inner tissue. 



If the rupturing takes place in succulent organs without any previous 

 dry period, due to a long continued supply of water in damp surroundings, 

 the torn places, as a rule, differ from those due to drought, in that, in the 

 latter, the wounded surface turns to cork or is cut off by a new cork layer. 

 In the former, on the other hand, the parenchyma cells, exposed by the 

 rupture, remain thin walled, at times elongated into pouches and decaying 

 easily. Boussingault found that the fruits lost sugar to Ihis excessive water. 

 This loss of sugar together with the increased absorption of water may 

 explain the watery taste of the fruit after rainy weather. Some blossoms, 

 left under water, also lost sugar. On the other hand, in sugar beets, rape, 

 in the seedling roots of wheat, barley and maize no sugar was lost although 

 the tissue was rich in sugar. 



There is a method of storing zvinter apples which is well worth recom- 

 mending, viz., placing the fruit in layers in sand. If the sand is kept too 

 moist, a large percentage of the fruit may lose in selling value because the 

 skin ruptures. 



Miiller-Thurgau^ made similar observations in related experiments. 

 After apples had lain eight months in boxes of earth he found the fruit was 

 wet, some of it ruptured, some mealy, and its acid and sugar content much 

 lower. The percentage of decaying apples was much less, however, than in 

 fruit lying free in the cellar. 



The rupturing of fruits and vegetables, due to storage methods, can be 

 overcome by supplying a dry, well ventilated place. In fruit on the tree, 

 especially the tgg plum which is very delicate, it is advisable in longer 

 periods of rain to shake the water from the tops of the trees. 



Finally, attention must still be called to the fact that the tendency to 

 rupture can also become hereditary. An observation of this was made with 

 cucumbers-. In forcing these, the owner always chose for his seed the 

 finest specimens of a variety which ruptured easily, and observed that this 

 bad condition manifested itself more abundantly and earlier from year to 



1 Fiinfter Jahresb. d. deutsch-schweizerischen Versuchsstation zu. Wadensweil. 

 Zurich, 1896. 



2 Zeitschr. f. Pflanzenkrankh. 1899, p. 183. 



