5° 



THE FACTORS [Part I 



after year ripened more and more rapidly, so that in 1857 it was harvested 90 days 

 after sowing. Seed of the same maize from Breslau, sown in the same bed and 

 at the same time as the former, took 122 days to ripen \' 



Twicrs of woody plants behave in the same way as seeds. A. de CandoUe 

 kept twigs of Popukis alba, Carpinus Betulus, Catalpa bignonioides, and 

 Liriodendron Tulipifera, some of which had grown in Montpellier and others 

 in Geneva, from February 4 onwards, in a frame, the temperature of which 

 varied between 7" and jo° C. The twigs from Geneva produced leaves 

 earlier than those from Montpellier. 



By means of such observations as these the existence of a hmitec 

 acchmatization has been demonstrated beyond doubt. More extendec 

 and exact investigations are necessary to determine the amplitude of tht 

 possible oscillations of the several cardinal points. 



In regard to the acclimatization of important forest trees in Europe 

 North America, and Japan, H. Mayr - has collected information, whidj 

 may claim wide interest as bearing upon the general question of naturaliza' 

 tion. According to this evidence most woody species enjoy good healtl 

 when they are transferred to a climate slightly zvarvicr than that of thei 

 native home. He says : — 



' Broad-leaved trees easily adapt themselves to a warmer climate b}- prolongin; 

 their whole course of development ; our native oak (Quercus pedunculata) whei 

 brought from its moderately warm home into the climatically allied region of th 

 subtropical zone, for example into California, at first grows very fast, and in th 

 similar climatic zone of Australia attains a height of 7 meters in nine years. Japanes 

 oaks (Quercus glandulifera and serrata) used for charcoal-making are extensive! 

 grown as coppice in the subtropical area of Japan, where in eight years the 

 become as tall as in fifteen years in their own home. Paulownia imperialis, rar 

 specimens of which grow well in the warm deciduous mountain forests of Japar 

 is cultivated for the sake of its wood in the subtropical region, where in virtue of it 

 extraordinarily rapid growth it produces a verj' light wood, which neither warps nc 

 shrinks. The tree repays cultivation better in the latter place than in its own honu 

 but it is already exhausted after twenty years, becomes hollow and dies, whereas i 

 its home, until recently, trees 6-7 meters in girth and 48 meters up to the crow 

 were not rare. 



' In the same way, plants transferred from subtropical zones into the tropii 

 exhibit an increased power of growth in the first decades. The Japanese camphoi 

 tree, for instance, belongs to the subtropical zone of evergreens ; in the tropin 

 of India and Java it grows remarkably fast ; its vigour of growth causes the stei 

 to divide into innumerable strong branches, so that the tree loses its ancestral forr 

 It is very probable that, owing to this accelerated growth during youth, an earlit 

 consumption of vitality and an earher natural death is brought about : for remar! 

 ably early and excessive production of seed characterizes all kinds of woody specit 



Schuebeler, op. cit., p. So. Many cases of expedited or delayed development are gi\t 

 by H. Hoffmann. -- h. Mayr, op. cit., pp. 365-368. 



