The natural history of plants, their forms, growth, reproduction, and distribution; . everal metres high above the ground on thebanks of streams. It must also be remembered that the woody growths close tothe ground in high Alpine regions are very often established on steep places, wherethe snow could not easily lie, could in no instance be deeply piled up, and could notexert a pressure on the stems and branches. The delicate Thyme-leaved Willow{Salix serpyllifolia) nestles with an especial predilection to the surfaces of rocks,and covers them with an actual carpet, and the Buckthorn (Rhavmus p
The natural history of plants, their forms, growth, reproduction, and distribution; . everal metres high above the ground on thebanks of streams. It must also be remembered that the woody growths close tothe ground in high Alpine regions are very often established on steep places, wherethe snow could not easily lie, could in no instance be deeply piled up, and could notexert a pressure on the stems and branches. The delicate Thyme-leaved Willow{Salix serpyllifolia) nestles with an especial predilection to the surfaces of rocks,and covers them with an actual carpet, and the Buckthorn (Rhavmus puviila) isfound exclusively on steep declivities, where it roots in the crevices of the narrow 524 INFLUENCE OF HEAT ON CONFIGURATION AND DISTRIBUTION OF PLANTS. rock gulleys, and growing out from them overspreads like ivy the vertical rock-faces. In all these cases it is certain that the weight of snow cannot have any deter-mining influence upon the form of the plants, and some other explanation must besought. May it not be perhaps that strong winds render it impossible for woody. .7(/t^-y vu Fig. 131.—Alpine Willows with stems and branches cliugini, to the ground in the TyroL plants with erect stems to grow in high Alpine regions? Observing the mist andvolumes of clouds rushing across the tops of the mountains, one gets some idea ofthe strength of the air currents which operate there, and whoever has experiencedthe effects of a storm on a high mountain ridge can estimate the force of the power-ful gusts of wind. And yet it would be erroneous to suppose that the force of thestorms on lofty mountain heights is greater than in mere hill regions. In the caseof many winds it is even certain that they increase in violence as they rush down INFLUENCE OF HEAT ON CONFIGURATION AND DISTRIBUTION OF PLANTS. 525 from the mountain ridge deeper into the valley. The Fohn-wind in the Alps oftenappears on the heights as only a slight breeze, but accelerates its velocity as it entersthe valle
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
