COMPAKATIVE WEIGHT AND COLOR OF FOLIAGE. 89 



spi-ayed uiid the other not. These were trees No. 10 of rows 20 and 

 21. Tree No. 10 of row 21 was sprayed the lii-st week in Mareh, 1S!»5, 

 with Bordeaux mixture (5 pounds copper sulphate, 5 pounds lime). 

 Tree No. 10 of row 20 had not been sprayed. From each of these trees 

 was gathered 2 pounds of healthy foliage. Careful measurements* 

 were made of the length of the branches of 1894 growth necessary to 

 yield this weight of healthy leaves, and it was found that on the 

 unsprayed tree it required 180 feet 2 inches, while on the sprayed tree 

 it requii-«>d only 49 feet 4 inches. The work was done as similarly as 

 possible on both trees. The 2 pounds of foliage from the sprayed 

 tree contained 2,428 leaves, and the 2 pounds from the unsprayed tree 

 2,546. In other words, 118 more healthy leaves were required from 

 the unsprayed tree than from the sprayed tree to equal 2 pounds in 

 weight, or 59 more leaves per pound. This result is due to the indi- 

 rect rather than the direct action of the disease. The leaves from the 

 unsprayed trees, being healthy, should average as great in weight as 

 those from the sprayed trees, were it not for the retarding and 

 impoverishing action of the disease upon the general growth of the 

 tree. In comparing diseased with healthy leaves, however, this ratio 

 would be reversed. The number of diseased leaves required for a 

 given weight would be nuit-h less than the number of healthy leaves 

 required. The diseased leaves are greatly curled and distorted through 

 the irritation or stimulative action of the fungus present in the tissues, 

 and in many instances they also become enormously increased in width, 

 thickness, and weight. 



The contrast observed in the color and general appearance of the 

 leaves of the sprayed and unsprayed trees was very marked. The 

 foliage of the trees treated with the stronger copper sprays, especially 

 the Bordeaux mixtures, presented the finest appearance. On May 8, 

 1895, two months after the spray work was completed, and at the 

 height of the disease, the foliage on trees thus sprayed presented the 

 greatest perfection. It was so abundant and so dense as to throw 

 very dark shadows beneath the trees, making it difficult to obtain 

 good photographs among them. This dense foliage existed upon both 

 the lower and the upper branches. The leaves were of a very dark 

 and rich green color, long, soft, and beautiful. Upon the unsprayed 

 trees comparatively few leaves presented the appearance of full 

 health, and much of the diseased foliage had already fallen, leaving 

 many trees nearly bare. The color of much of the remaining foli- 

 age was yellow and sickly. Many of the uncurled leaves were small 

 and light colored on both the lower and the upper limbs. What 

 growth these trees had made up to that date was largely terminal, very 

 little healthy or comparatively healthy growth being apparent from 

 lateral buds. (Compare Pis. VIII and IX.) 



