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BULLETIN 395, IT. S. DEPAKTMENT OP AGRTCULTUEE, 



tions suitable for infection. These conditions led to the development 

 of a special technique, of which the following is a brief outhne: 



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 (PI. Ill, 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 satisfacr 

 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), wluch 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 li- 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 wMch 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. ) 



