TREE PLANTING ON STREETS AND HIGHWAYS. 121 



Mr. Joseph Wharton, in an article, "Observations upon Autumnal Foliage" 

 {American Journal of Science, Vol. 47, p. 253), says that the distinguished French 

 chemist Fremy "separates chlorophyll, when dissolved in alcohol, into two coloring 

 matters, by submitting it to a mixture of ether and chlorohydric acid ; the former 

 takes up the yellow matter (phylloxanthin), the latter the blue matter (phyllocyanin), 

 each liquid having distinctly the yellow and the blue color respectively, which being 

 mixed by shaking together form a leaf green. The yellow coloring matter of new 

 sprouts and of etiolated leaves contains phylloxanthin, capable of being developed 

 into chlorophyll; in autumnal yellow leaves the phyllocyanin has been destroyed. 

 The yellow matter, Fremy supposes to be more stable than the blue." 



Mention is also made in scientific works of chemists who succeeded in extract- 

 ing from green leaves pigments of various colors in the form of dried, powdery 

 substances. 



All these explanations, simply stated and divested of technical phrases, might 

 read something like this: The substance in a live leaf contains blue and yellow pig- 

 ments, and, as is well known, these colors when mixed form green. When, through 

 failing vitality the action of these pigments is no longer restrained by the presence 

 of chlorophyll, their colors become apparent. True, no one ever saw a blue leaf ; 

 but this color, under the action of the acid remaining in the cell-sap of the leaf, will 

 be stained red. If the yellow substance alone remains the leaf will display that 

 color; and with acids, orange. If the pigmentary substances are absorbed before 

 the leaf falls, the brown walls of the empty cells will give it a russet tint. This 

 explanation is not scientific, and it may not be entirely accurate ; but it is fairly 

 deducible from the various and varying statements of the botanists and chemists 

 who have made this subject a matter of scientific research. 



Influence of Frost. 



There is a popular impression that the autumnal change of leaf color is due to 

 the action of frost ; and that early frosts conduce to a more vivid tinting of the 

 foliage. This, however, is an error that a little thought and observation will correct. 

 Some of our trees display red and yellow leaves in August, long before cold weather 

 comes. The brightest red shown in all our autumn foliage is that of a Red Maple 

 on which the leaves turn color in August. 



Conceding that the intensity of color differs with the seasons, it may be said 

 that the most brilliant coloring of our forests occurs when a rainy summer is 

 followed by a cool, dry August and September in which there is no frost. Undoubt- 



