332 FIELD AND WOODLAND PLANTS 



where they can be safely stored for the winter. The leaves, thus 

 impoverished, become mere skeletons — mere collections of empty, 

 hfeless cells ; and if no further change takes place, they assume a 

 very pale colour, hke the leaves of the Hornbeam, Birch, and the 

 Willows. 



But the transfer of the nutrient matter from leaf to stem or 

 root is accompanied by numerous chemical changes by which new 

 compounds are formed. Among these new substances a dark blue 

 compound called anthocyanin is produced in some plants ; and 

 where this exists in considerable quantities we find the leaves of 

 a dark bluish-green colour, like that of the autumn foliage of the 

 Pine. 



Acids are also sometimes formed as a result of the complicated 

 chemical changes that take place during the transfer above described; 

 and these react on the anthocyanin present, changing its colour to 

 a tint that varies according to the proportion and quantity in 

 which they exist. 



Thus, if anthocyanin is present, together with a small amount 

 of acid, the leaves are turned violet, as in the case of the autumn 

 leaves of the Dogwood and the Spindle Tree ; or purple, like those 

 of the Service Tree. A larger proiDortion of acid produces, with the 

 anthocyanin, the brownish green tint of the Alder leaves ; or the 

 brownish yellow of the Oak ; while still larger proportions will 

 turn the anthocyanin yellow, orange, red, or scarlet, according to 

 the quantity in which the latter is present. Thus we can account 

 for the rich yellow of the Maple in autumn, the orange of the Aspen 

 leaves, the beautiful scarlet tints of the Mountain Ash and the 

 Barberry, and the grand display of varied colours exhibited by the 

 autumn Beeches. 



Again, before the leaves are shed, the buds that are destined 

 to produce the new branches of the following spring are aheady 

 formed. These may be seen on all deciduous trees and shrubs, 

 some of them in the axils of the leaves, and others at the tips of the 

 present twigs. Each bud is the embryo branch of the following 

 year. Some of them are destined to produce leafy branches only ; 

 some are to develop into branches bearing both floral leaves and 

 flowers ; while others are to produce flowers mthout floral leaves ; 

 and it is interesting to note that, even at this stage, sections of the 

 buds, examined with the aid of a microscope, \^ill reveal the 

 future leaves and flowers compactly concealed within their scaly, 

 protective coverings. 



