34° 



The Museum Gazette 



AUTUMN LEAVES. 



The influences under which the changes in colour of leaves 

 in autumn are brought about, may be placed in several groups. 

 In all of them some lowering of standard of health is involved. 

 If a green leaf retains its full vigour it remains green, but 

 any interference with that vigour will be followed by change 

 in colour. What the change may be will depend upon the 

 original constitution of the plant. The Virginian creeper will 

 produce scarlet, the beech mahogany brown, the elm yellow, 

 and so on. The commonest of all causes of change is simply 

 age. The leaf has become senile and is about to die. In 

 this case all the leaves on the same branch will suffer more 

 or less together, and usually all in the same manner. The 

 changes in colour will begin at the top and edges of the leaf, 

 and will affect all parts of it, that is, they will have bilateral 

 symmetry. The parts last to change will be those nearest 

 the mid-rib and large side " veins." These structures carry 

 the sap tubes, and supply best the parts nearest to them. 

 In many cases a very beautiful pattern is produced by the 

 green bands which remain to the last placed in symmetry on 

 each side the mid-rib. Next to the top and borders, the 

 parts which change colour are broad, ill-margined bands 

 between the veins. This statement is, of course, only 

 another way of saying that the veins keep green the longest. 



Next in importance to age we have the influence of injuries. 

 These may be either of the leaf itself or of its footstalk, or 

 of the twig on which it is borne. If the stem or footstalk 

 be damaged the natuial onflow of sap may be diminished, 

 and the part of leaf supplied will certainly change colour. 

 If it be part of the footstalk of the leaf itself it may be that 

 only one half of the leaf will change, but if the twig is 

 involved, then the whole leaf will suffer, and the changes 



