New ¥ork AGRICULTURAL EXPERIMENT Srarton. 463 
it is difficult to furnish accurate, specific evidence as proof of 
the above statement. Reliance must be placed upon the ac- 
curacy of observation of the experimenters. Since, however, 
leaf characters reflect:so delicately the health of a plant, it 
does not need even the accuracy of a practiced eye to gauge. 
the well-being of a tree from the leaves. 
Color of foliage.—It required only a glance to detect a dif- 
ference in the color of the foliage in the two plats and to note 
that something was amiss with the leaves of the sodded trees. 
The dark and rich green of the tilled trees indicated an abund- 
ance of food and moisture and the heyday of health, while the 
pale and sickly foliage of the sodded trees suggested drouth, 
starvation or some serious physiological disturbance. To the 
casual visitor this was the most apparent sign of the superior- 
ity of tillage and more than one man of the hundreds who 
visited the orchard was heard to say as his eyes lighted on the 
contrasting colors of tilled and sodded trees, “that satisfies 
me.” The absence of color in the leaves of the sod-mulch trees 
is due to a lack of chlorophyll or leaf-green. Chlorophyll is 
essential to the assimilation of plant food and without a suf- 
ficient quantity plants must suffer from mal-nutrition. Its lack 
must be counted as both a cause and an effect of the ill-health 
of the sodded trees. 
Area of foliage.—No feasible plan could be found for taking 
the leaf area of individual leaves, the total leaf area, or the 
number of leaves on the trees in the two plats. But here again 
it was easy to see that the leaves of the tilled trees were much 
larger, and much more numerous, and that therefore their 
total leaf area was much greater. In fact some practical 
orchardists found fault with the foliage of the tilled trees, 
saying that the size and number of the leaves indicated too 
much wood growth and shut out sunlight thus preventing the 
proper coloring of the tilled fruit. 
Weight of foliage-—The comparative weights of the leaves 
in the two plats were ascertained as follows: Groups of 10 
leaves each from the ends of the shoots on 5 sides of 48 trees in 
each plat were taken—2,400 leaves from sodded and the same 
