J. Wharton on Autumnal Foliage. 253 
nourished and succulent, while the inner leaves—those nearer 
the trunk—are smaller and weaker. It is not uncommon fora 
Sassafras tree, which stands alone, to present in the autumn 
the appearance of a green mass of foliage, illuminated from 
within by red and yellow lights: this results from the com- 
plete change of those feeble leaves in the interior, before the 
more vigorous outward leaves are in a condition to yield. 
tree, observed last Fall, afforded a similar illustra- 
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y by a process similar to that which separates the single 
leat from the plant, and whose first effect had of course been an 
untimely stoppage of the circulation.* 
eaves which die in the Summer are usually dried out di- 
rectly, or, if the weather is moist, are quickly rotted ; still, it 
18 common enough to see single dead leaves of Gum, Sumac, 
or Sassafras, splendidly reddened many weeks before a frost. 
Tn June, 1868, I observed leaves of Mahonia upon a sickly 
twig thus colored, and on July 19th, I found thoroughly red- 
dened leaves of Sassafras and Gum, and leaves of American 
Poplar and Chestnut of perfect autumnal yellow ; all being of 
_ Course such as by feebleness of, or injury to, the sustaining 
twigs, had been deprived of their circulation. . 
It is somewhat remarkable, however, that of the millions of 
dead leaves which I saw last Summer upon twigs wounded by the 
Seventeen year locusts, not one showed autumnal tints; though 
T observed upon a number of trees, bearing the brown leaves of 
the locust-wounded twigs, an occasional leaf of a full autum- 
ted upon a twig not so wounded. 
For the convenience of those who may incline to pursue this 
Subject, I add a compend of some of the principal recent inves- 
tions concerning chlorophyl and related matters 
Comptes Rendus, 1, 405. Frémy separates chlorop 
es, which first occurs in the parietes of the ves The cells in 
multiply, till at last the vessels are completely choked up in the neigh 
the insertion leaf, and thus a di ial plane is formed, across 
leaf U of the us @ differen 
Stalk breaks, and the leaf accordingly falls. 
