1881.] NATURAL SCIENCES OF PHILADELPHIA. 455 



the American allies color, while the European rarely do. He 

 named on the American side, Betula populifolia^ Fraxinus sambuci- 

 folia, Quercus alba^ Crataegus cordata^ Ulmus Americana, Alnus 

 serridata, Castanea Americana^ as against Betula alba, Fraxinus 

 excelsior, Quercus Robur, Crataegus oxyacantha, Ulmus cam- 

 pestris, Alnus glutinosa and Castanea vesca. The whole Ameri- 

 can line had autumn coloring, of which the parallel European 

 line was wholl}^ destitute. These trees did not lose this character- 

 istic by removal to the other continent. In America there were 

 many of the European species five or ten generations from seed, 

 and yet these last genei'ations showed no more disposition to 

 embrace the color characteristics of their American cousins, 

 than did the first progenitor brought from abroad. We were 

 so accustomed to associate our bright clear autumn skies with 

 the color of our autumn foliage, that facts like these stagger us. 

 Wh}' should several generations of these European trees resist 

 our climatal influences ? But we have to remember that the coloi*- 

 ing of fruits and foliage is not wholl}- the result of chemical power ; 

 what for want of a better name we know as vital power, claims 

 a share. 



Some apples have color on the sunny side, while the I'osy cheek 

 never appears on those of the same variet}' hidden b^^ the foliage, 

 and in these cases ib is self-evident sunlight is a cause of color. 

 Yet if we pluck such a variety from the tree, and place it in the 

 sunlight, it will not color, so that we see here that there must be 

 a connection with the living principle in the tree to enable the 

 solar ra3^s to act. Yet it requires a relaxation of the leaf's hold 

 on life to bring out these colors. At any time during the summer, 

 a maturing leaf on an American tree exhibits bright color — yet it 

 a djnug leaf half-colored, be plucked from the parent stem, there 

 is no further change in the tint. Mau}^ leaves pass through grades, 

 as green, light yellow, orange, brown, to scarlet. If they are 

 gathered at yellow or brown, the3- remain 3^ellow or brown, and 

 so on all through these stages. Coloring therefore, could not 

 whollj'^ be considered chemically, for though deca}^, Avhieh we take 

 to be a chemical action, is going on during the coloring stage, 

 complete separation from the living tree at once stops the process. 



If we consider these two facts together, and then some other 

 known natural laws, we may form some reasonable hypothesis. 

 There is, for instance, the principle of heredity, so ably insisted 

 on b}^ Mr. Darwin, in connection with all living things. A force 

 once applied to an object, exerts an influence after the power has 

 been removed. A Avheel runs round, after the hand which turns 

 it is taken away, and a change in a plant brought about by any 

 circumstance will continue in connection with that plant some 

 generations after the circumstances have ceased to exist. That 

 this is so has been proved by Naudin with hybrid, or perhaps we 

 should say crossed, lettuces, and in other ways. Supposing then 



