104 ARISTOCRATS OF THE GARDEN 



the leaf-blade into the woody branches or subter- 

 ranean rootstock and there stored, chiefly in the form 

 of starch, until the season of growth re-commences 

 the following spring. The leaves from which every- 

 thing useful has been transported form nothing more 

 than a framework of cell-chambers containing merely 

 waste products, like crystals of calcium oxalate, 

 which are thrown off with the leaves and help to en- 

 rich the soil. But while the process of food evacua- 

 tion is going on other changes take place. In many 

 plants a chemical substance known technically as 

 anthocyanin is produced in the leaves, and often to 

 such an extent as to become plainly visible on the 

 exterior. It appears red in the presence of free acids 

 in the cell-sap, blue when no acids are present, and 

 violet when the quantity of acids is small. In a great 

 many leaves the bodies which contain the green color- 

 ing matter become changed to yellow granules while 

 the evacuation of food substances is in process. 

 Sometimes these granules are very few and antho- 

 cyanin is absent; then the leaf exhibits little outward 

 change except losing its freshness before it falls. 

 In others the yellow granules are abundantly de- 

 veloped and if anthocyanin is absent, or nearly so, 

 the whole leaf assumes a clear yellow hue. If there 

 is an abundance of yellow granules together with 



