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 the plant must cease. 



The results attained by Halt do not entirely agree with any of the 

 preceding. He finds that the precipitation 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 affected 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 temperature. {Z. 0. G.M.^ xix, 

 p. 139.) 



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

 pendence of the growth of wood upon meteorologic;d factors : 



1. Temperature and precipitation are the meteorological phenomena 

 that affect the process of the formation of wood. 



2. Of these two variable quantities during the i)rincipal 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 influence 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 affected in the same degree 

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

 perature. 



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

 fluence, the other being inactiv^e. 



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

 duration of insolation. 



8. The increase of carbonaceous compounds goes parallel 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. M., 

 XIX, p. 93.) 



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

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

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

 finds that the difference in vegetation is due not to the difference in 

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



