i68 



THE BOOK OF NATURE STUDY 



Looking down from a height of two thousand feet it is possible to 

 tell by the colouring the limit of the oak on the hillside, and to 

 recognise even at a distance the greater height above the sea- 

 level at which the beech is found, at any rate in some counties. 

 Most trees have their distinctive autumn tints ; the hornbeam turns 

 from green to yellow, then ruddy gold, and finally a rusty red, the 

 tint that persists throughout the winter. This change of colour is 

 due to the breaking up of the chlorophyll granules, owing to the lower 

 temperature combined with the less intense light . Brown, yellow, or 



red pigments are 

 thus formed, and 

 give the character- 

 istic colour to the 

 tree. This change of 

 colour is followed, 

 in the majority of 

 trees, by a falling of 

 the leaves. The time 

 of leaf-fall varies 

 with different trees. 

 The ash, though 

 one of the latest to 

 burst into leaf, loses 

 its leaves first ; the 

 beech may retain 

 its leaves on its 

 lower branches 

 throughout the 

 winter. The elm 

 gets a dull dark 

 green tint, then 

 orange, after that 

 pale yellow, before 

 its leaves begin to 

 fall, and the rapid- 

 ity with which the 



FIG. 48. Two-year-old twig of Oak. s, Scar of attachment of tree is Stripped of its 

 last year's leaves ; ss, scars left by scales of last year's bud, 

 marking the limit of a year's growth. foliage is noticeable . 



