LEAP-FALL TJ 



A number of shrubs and trees, however, appear clothed with 

 green leaves at all times of the year. These are described as ever- 

 green. In such plants the leaves produced from buds in spring are 

 not shed in the following autumn or winter, but live sometimes 

 several seasons before they die and fall off. The length of time 

 during which the leaf remains on a so-called evergreen tree after 

 it is produced depends upon the kind of tree, the climate, 

 situation, soil and other conditions. 



In privet the leaves often remain on the twigs during winter, 

 and fall off when the new buds open in spring ; while in some 

 conifers the leaves are not shed until they are ten years old or 

 more. 



The leaf usually separates from the shoot bearing it, at a point 

 close up to the latter, and a more or less conspicuous mark, 

 termed the leaf-scar, is left upon the shoot. The dangerous 

 effects of an open wound is prevented by the formation of a 

 protective layer of cork over the surface of the scar, which 

 layer originates some time before the actual fall of the leaf. 



Leaf-fall is not merely the dropping off of dead, withered 

 leaves, but a distinct physiological process, which does not 

 take place in leaves which are prematurely killed by the action 

 of frost or excessive heat. Moreover, the leaves do not fall off 

 from branches of trees and shrubs broken or cut off, in early 

 summer. 



Ex. 42. — Observe the manner of leaf-fall upon the common shrubs and trees, 

 paying special attention to those with compound leaves, such as ash and 

 horse chestnut. 



Note the form and size of the leaf-scars. 



Try and determine how long the leaves persist upon box, laurel, privet, 

 holly, silver-fir, Scotch pine, and other common evergreen shrubs and trees. 



