126 



end of the rainy period, when the rainfalls became less frequent, the 

 percentage rose to nearly its former value. On the other hand there 

 was a regular diminution of the other elements that were not sugar, 

 and consequently an improvement in the percentage of purity. There- 

 fore a permanent injurious influence of the heavy rainfall on the 

 quality of the beet was not proven. 



Grassmann (1887) also confirms the results of Girard to the effect 

 that the sugar once formed in the beet remains there, no matter what 

 the further growth may be. There the diminution of the percentage 

 of sugar after a rainfall is only relative in that the sugar is dissolved 

 in more sap, and this is distributed throughout a greater mass of beet ; 

 the sugar, and with it the percentage of purity, sinks only very lit- 

 tle after the first rainy day, but on the second sinks more considera- 

 bly and then slowly rises from the third to the fifth day. (See 

 Wollny, X, p. 300.) 



Now that the previous studies have shown the importance in agri- 

 culture of the quantity of available water the question still remains 

 whether the results of these experiments are directly applicable to 

 determining the influence of rainfall on vegetation under the natural 

 climatic conditions. We could in advance answer this question in 

 the negative, inasmuch as the precipitation is never so uniform as"the 

 water artificially supplied in these experiments, as also because the 

 utilization of the natural rainfall by the earth varies with the physi- 

 cal properties of the latter; but by a closer consideration one is led to 

 the conclusion that in spite of the departure from natural conditions 

 still the results of these experiments do allow us to draw many con- 

 clusions as to the influence of rainfall on the growth of cultivated 

 useful plants, especially when we leave out of consideration the effect 

 of the water at different epochs of vegetation and the peculiarities of 

 the capacity of the soil for water, and at first study only the average 

 character of the climate as depending on the amount of precipitation 

 and consider the weather during the growing season. 



