CHAPTER II 



PERIODIC PHENOMENA OF VEGETATION WITHIN 

 THE TEMPERATE ZONES 



Introduction. i. Metabolism and Interchange of Energy in Mesotherniic 

 Plants at Different Seasons, i. Periodicity in the gean-trce. Processes that are 

 visible externally. Development of the flower-buds in the gean-tree. Crand periods and 

 temperature. Season of rest and temperature. Carbohydrates in the periods of activity 

 and repose. Effects of temperature on the solution and re-formation of starch, ii. Starch- 

 trees and Fat-trees. Causes of the formation and disappearance of fat. iii. Theory of 

 Forcing. The two conditions of protoplasm. The resting condition prolonged by low 

 temperatures. Suppression of growth in length. Oecological optimum temperature in 

 the active period coinciding with the natural temperature, iv. Periodicity of Herbaceous 

 Plants. The sweetening of potatoes, v. Cold and Drought. Similar effects of winter 

 period and dry period. 2. Periodic Aspects of Vegetation, i. General Considerations. 

 Winter phenomena. Plants flowering in winter in Japan. Cold and the development 

 of flowers, ii. Periodic Phenomena in the South Temperate Zone. Chili. South 

 Africa. South Australia. 



IXTRODUCTION. 



E\EX at a short distance outside the tropics, indeed occasionally within 

 them, for instance in South China, the periodic change of temperature 

 makes its influence felt on vegetation. With otherwise equally favour- 

 able conditions as regards moisture a retardation in the phenomena 

 of plant-life is unmistakable, and the times of flowering are rigidly 

 associated with the alternation of cold and hot season.s. Such dependence 

 is specially evident in plants when they are transplanted from higher into 

 lower latitudes. Thus the periodic phenomena of introduced Central 

 European broad-leaved trees in Madeira, w-here the mean temperature 

 of the coldest month (January) is 1.5° C. and that of the hottest (August) 

 ii-z" C., resemble those in their native country ; and Viola odorata in Santa 

 Catharina (South Brazil) produces its cntomophilous flowers, according to 

 F. Miiller, from March until December, but at the height of summer 

 usually bears cleistogamous flowers only. 



The lower the winter temperatures, the greater of course becomes the 

 difference in the vegetation in the cold and hot seasons respectively, in 

 particular where there is a moist summer-climate. In districts with a 

 drj' summer, for instance the steppes, and to a still greater degree in 



