METEOROLOGY. 391 



temperature accelerates the development up to a certain limit, which is 

 the best temperature ; every increase above this retards the develop- 

 ment up to a certain limit, which is the maximum possible, beyond which 

 the growth of tiie plant must cease. 



The results attained by Hult <lo not entirely aiiree with any of the 

 [)receding. He tinds that the pre('-ii)itation in Sweden is nowhere so 

 slight that vegetation is regularly restricted, nowhere so great that 

 the blossoming or leafing is disturbed, but the ripening of the fruit 

 occurs at the season of greatest rainfall, and this stage of plant growth 

 is aflected by the rain. The blossoming of any plant throughout the 

 whole of Sweden occurs at the same temperature, but when we pass to 

 Lapland and Jempland, the very rapid progress of the spring tempera- 

 ture cannot be followed by the plant, and the blossoming occurs subse- 

 quent to the occurrence of the normal temi)erature. {Z. 0. G.JL, xix, 

 p. 139.) 



422. A. Spamer communicates the following conclusions as to the de- 

 pendence of the growth of w^ood upon meteorological factors : 



1. Temperature and precipitation are the meteorological phenomen.'i 

 that affect the process of the formation of wood. 



2. Of these two variable quantities during the priuci{)al period of 

 growth, the rainfall diminishes the formation of wood while the heat 

 increases it. 



3. The principal period of wood growth is from July to October, at 

 least for the plants which are very sensitive to frost. 



4. The rainfall seems to intlueuce growth more than the temperature. 

 [Excess of rain diminishes growth more than excess of temperature in- 

 creases it.J 



5. The growth of different plants is not aftected in the same degree 

 by the rain ; some are affected more by rain and others by the tem- 

 perature. 



G. In many i)eriods only one of these factors appear to exert any in- 

 fluence, the other being inactive. 



7. Possibly this anomaly may be explained by observations of the 

 duration of insolation. 



8. The increase of carbonaceous compounds goes paralhd with the in- 

 crease in the inorganic constituents of the wood. 



9. The aqueous component of the wood diminishes when the carbon- 

 aceous increases. 



10. The so-called ripe wood [the heartwood] differs from that which 

 is less ripe by a greater amount of ashes and carbon. {Z. 0. G. i)/., 

 XIX, ]). 93.) 



423. M. Bergmans, of Flushing, has studied the dillerence between 

 sea and continental climates as shown by the vegetation, especially by 

 a study of the jdants ordinarily cultivated in the temperate zone. He 

 tinds that the difierence in vegetation is due not to the difference in 

 wiean temperature but to the difference in the amount of sunshine ; clear 



