22 
BULLETIN 395, U. S. DEPARTMENT OF AGRICULTURE, 
tions suitable for infection. These conditions led to the development 
of a special technique, of which the following is a brief outline : 
In order to overcome the first of these difficulties the fruits used for the inoculations 
were bagged as soon as practicable after the shedding of the calyces, and were kept 
protected in this manner throughout the course of the experiments; the number of 
controls was made as large as circumstances permitted; and the inoculations were 
made in numerous corroborative series upon areas least subject to natural infection, 
about one-half of the total number being made upon the protected equatorial sur- 
faces, which are normally free from natu- 
ral infection, even under the most severe 
conditions (PL III, fig. 1). 
The bags used were made to order from 
a thin, translucent, partially waterproofed 
(glassine) paper. They were 11 inches 
wide and 14 inches long, but 12 by 16 
inches proved later to be a more con- 
venient size. 
In order to secure at will favorable 
conditions for infection it became neces- 
sary to devise a method for the satisfac- 
tory regulation of moisture. In continu- 
ation of preliminary experiments made 
in 1912 a very simple and satisfactory 
contrivance was developed. It was even 
better adapted to twig than to fruit inocu- 
lations and should be capable of general 
adaptation in inoculation work of this 
type, where moisture is a limiting factor 
and where it is impracticable to conduct 
the experiments in moist compartments. 
The apparatus, which works by capil- 
larity, is readily understood by reference 
to figure 6. One end of a wick of wet 
absorbent cotton (A) is appressed to the 
area to be moistened, while the other end 
extends through a small orifice in a cork (B) into a water container (C), which is 
attached by means of a soft tape (D) to some convenient part of the host. The size 
and shape of the container may be adapted to suit the convenience of the operator. 
Lipped test tubes, 18 by 150 mm., were used in the earlier experiments, because they 
were the only suitable apparatus available at the time. They were quite satisfac- 
tory, but small, light, lipped flasks later proved more desirable, as they are more 
capacious and render the device more compact. 
With the apparatus used it was found practicable to keep twig inoculations thor- 
oughly moistened for two weeks without refilling, while a moist zone three-fourths of 
an inch wide could be maintained about a peach lh inches in diameter for four days. 
The container is refilled easily by removing the cork, without disturbing the arrange- 
ment of the upper portion of the wick. For convenience of attachment it is distinctly 
advantageous to allow the wick to enter the container from one side of the cork 
rather than from the center, while corks cut as shown in figure 6 (E) are easily 
manipulated and are unlikely to abrade the adjacent tissues of the fruit. If the wick 
fits loosely in the orifice or if the cork is lightly inserted in the flask, no strain is 
exerted upon the fruit by the swaying of the water container by the wind. Any such 
lateral motion is readily taken up by the short section of the wick which extends 
Fig. 6.— Device for supplying moisture for outdoor 
inoculations: A, Wick of absorbent cotton; B, 
cork; C, water container; D, attachment to host; 
E, enlargement of B. (A to D are about one- 
half natural size.) 
