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In this case it would scarcely be denied that a relatively dry or 

 moist climate or any similar modification of the weather should exert 

 an influence on the vegetation similar to that exerted by the soils of 

 different moistures in the above-described experiments. We must 

 the more readily agree to this conclusion since, independently of the 

 fact that water belongs to the most important, indispensable, factor of 

 vegetation, it is also true that the observations on the growth of plants 

 made in climates having different degrees of moisture agree closely 

 with the views above explained. It is already well known in agri- 

 culture that in a dry climate the harvests are only scanty and to an 

 extraordinary degree dependent on the rainfall, and, furthermore, it 

 is well known how favorably the general condition of the plants is 

 affected by a moderately moist climate, and how, on the other hand, 

 the crops of cultivated lands are diminished by extremely large quan- 

 tities of rain, when in consequence of a large capacity of the soil for 

 water, a large quantity of water accumulates in it either temporarily 

 or for long periods of time. Furthermore, it is well known that the 

 stalk of the plants and the formation of straw are greater in pro- 

 portion as the climate is moister; that the various kinds of cereals in 

 dry regions produce a glassy, glutinous grain, but in moist lands a 

 mealy seed, poor in nitrogenous compounds. All these phenomena, 

 observed on a large scale in the life of the useful plants, make them- 

 selves felt also in a similar way in the experiments above quoted, and 

 therefore the results of the latter can with perfect justice be quoted 

 in deciding upon the questions lying at the base of our work. But 

 these present conclusions hold good only for the total rainfall during 

 the growing season, and it will be further necessary to fix in a similar 

 way, by experiments, the influence of precipitation during the indi- 

 vidual stages of growth of the plants, as also the relation of the soil 

 to the water, so as to' determine the influence of the ordinary natural 

 climatic conditions. 



