CLIMATE AND TREE GROWTH 117 



country to exhibit evidence of it if it existed. Larch 

 produces seed freely in the British Isles, and plantations 

 of various sizes may be seen descended from seed ripened 

 in the country. Yet these trees burst their buds in 

 March or April long before the temperature is sufficiently 

 high for growth to proceed ; whereas native trees either 

 remain quiescent until May, as oak, ash, beech, Scots pine, 

 etc., or are capable of withstanding the frost of March and 

 April with impunity, as alder, willow, poplar, birch, 

 hawthorn, etc. Horse chestnut, Norway maple, lime, 

 sycamore, and other early leafers, are sufficiently hardy, 

 however, to withstand most spring frosts without serious 

 injury, but suggesting, if not indicating, an acquaintance 

 with quicker and more decided spring temperatures than 

 they find in Britain. Instances of late growth in autumn 

 occur Avith such species as Rohinia, Zelkowa, Spanish 

 chestnut, etc., causing badly ripened shoots, and sub- 

 sequent injuries from early frost, and these habits do not 

 appear to be altered by long-continued growth in this 

 climate, although the older a tree becomes the less the 

 tendency to start or continue growth early or late. 



Another feature of plant life is the power of adaptation 

 to a new environment, enabling the plant to make certain 

 provisions against the risk incidental to heredity and 

 peculiar to an ancestral type. With successive generations 

 this process is progressive. The leafing of trees before 

 the arrival of normal growing temperatures, or their 

 growth after the approach of winter, may be regarded as 

 hereditary characters. The winter flowering of trees, as 

 hazel, birch, willow, poplar, ash, elm, alder, etc., is also 

 hereditary, and cannot be eliminated within limited periods 

 of time. Morphological or physiological adaptations, such 

 as the production of hairs, thickening of epidermis or 

 cuticle, production of midsummer shoots on oak, beech, 

 etc., reddening of needles during the winter months, 



