Book I. 



DISTRIBUTION OF VEGETABLES. 



265 



1693. The temperature of summer, as it varies only by the intensity of heat, is not pro- 

 ductive of so many injurious accidents as that of spring. Very liot dry summers, how- 

 ever, destroy many delicate plants, and especially those of cold climates. A very early 

 summer is injurious to the germination and progress of seeds ; a short summer to their 

 ripening, and the contrary. 



1694. Autumn i^ on important season for vegetation, as it respects the ripening of 

 seeds ; hence where that season is cold and humid, annual plants, which naturally flower 

 late, are never abundant, as in the polar regions ; the effect is less injurious to perennial 

 l)lants, which generally flower earlier. Frosts early in autumn are as injurious as thoso 

 which happen late in spring. Tlie conclusion, from these considerations, obviously is, 

 that temperate climates are more favorable to vegetation than such as are either extremely 

 cold or extremely hot. But the warmer climates, as Keith observes, are more favorable 

 upon the whole to vegetation than tlie colder, and that nearly in proportion to their 

 distance from the equator. The same plants, however, will grow in the same degree of 

 latitude, throughout all degrees of longitude, and also in correspondent latitudes on dif- 

 ferent sides of the equator ; the same species of plants, as some of tlie palms and others, 

 being found in Japan, India, Arabia, the West Indies, and part of South America, 

 which are all in nearly the same latitudes ; and the same species being also found in 

 Kamschatka, Germany, Great Britain, and the coast of Labrador, which are all also ia 

 nearly the same latitudes. ( Willdenow, p. 374.) 



1 695. Tke most remarkable circumstances respecting the temperature in the three zones, is 

 exhibited in the following Table by Humboldt. The temperature is taken according to 

 the centigrade thermometer. The fathom is 6 French feet, or 6,39453 English feet. 



1696. Elevation, or the height of the soil above the level of the sea, determines, in a very 

 marked manner, the habitation of plants. The temperature lessens in regular gradation^ 

 in the same manner as it does in receding from the equator, and six hundred feet of ele- 

 vation, De Candolle states, are deemed equal to one degree of latitude, and occasion a 

 diminution of temperature equal to 23^ of Fahrenheit; 300 feet being nearly equal to 

 half a degree. Mountains 1000 fathoms in height, at 46 of latitude, have the mean 

 temperature of Lapland ; mountains of the same height between the tropics enjoy the 

 temperature of Sicily ; and the summits of the lofty mountains of the Andes, even where 

 situated almost directly under Uie equator, are covered with snow as eternal as that of the 

 north pole. 



