188 , AUTUMNAL LEAVES. 



growth and development, and the facility with 

 which new chemical combinations are affected by 

 the physiological processes of plants as shown by 

 the endless variety in the chemical constitution of 

 vegetable products, we have no difficulty in com- 

 prehending the general causes which aid in pro- 

 ducing the colours of the vegetable world or the 

 extreme variability of these colours.' Further on 

 Mr. Wallace remarks : ' The different colours 

 exhibited by the foliage of plants and the changes 

 it undergoes during growth and decay, appear to 

 be due to the general laws already sketched out, 

 and to have little if any relation to the require- 

 ments of each species. But flowers and fruit 

 exhibit definite and well pronounced tints, often 

 varying from species to species, and more or less 

 clearly related to the habits and functions of the 

 plant.' 



But to return to the autumnal leaves of the 

 Oak. Grilpin, in his Forest Scenery, says : e Of 

 all the hues of Autumn, those of the Oak are 

 commonly the most harmonious. As its vernal 

 tints are more varied than those of other trees, so 

 are its autumnal. In an oaken wood vou see 



