WHITE-PINE BLISTER RUST. 41 



METHODS OF INOCULATING RISES. 



The methods of inocuhiting Ribes plants are not claimed to be 

 original with the writer or his associates. It is well known that 

 some of these methods have been in use for many years. They are 

 given here to show the conditions under which the experimental 

 work was done^, as follows: 



(1) WTien plenty of spore material is available, as is usually the case with a?cio- 

 spores, the spores may be placed in a considerable quantity of water and the top or 

 branch of the Ribes plant dipped into it. The spores will be distributed quite 

 evenly over all parts of the dipped plant. (See Clinton (12 j. ) This method was used 

 by the writer as early as 1909, and has been very successful. It uses up large 

 quantities of inoculum, however. 



(2) Another method which has been much used is to spray water from an atomizer 

 upon the part to be inoculated, then .shake the dry spores upon the wet surface. 

 This also requires a plentiful supply of inoculum. It has been a fa^'orite method, 

 as it giA'^es good results with reasonalde certainty. 



(3) When inoculating with urediniospores from fresh leaves, the part to be inocu- 

 lated is sprayed, and the leaf bearing the inoculum is turned with its lower surface 

 on that of the healthy leaf and the two rubbed lightly together. 



(4) If the inoculum is scanty, the spores are moistened with a drop of water and 

 lightly scraped off upon the moistened healthy leaf with a sterilized scalpel or knife 

 blade. 



(5) If the inoculum is in moderate quantity, the spores are placed in a small 

 quantity of water in a sterilized atomizer and sprayed upon the healthy plant. • 



(6) The spores, if faii-ly plentiful, are sometimes collected in a watch glass, a small 

 quantity of water added, and then a clean camel's-hair brush is dipped into the 

 mixture and brushed over the surface to be inoculated. With this method it is 

 advisable to wet the inoculated part with an atomizer after inoculation, or results 

 will be meager. 



(7) Occasionally healthy leaves have l)een rubbed or dipped in the spore mixture 

 described in paragraph 6. 



Gravatt made comparative tests of some of the foregoing methods 

 of applying the inoculum. This comparison showed one-fourth 

 more infection with method 5 than with method 6, Avith three 

 different species of Ribes. General experience has shown the order 

 of efficiency of the methods to be as follows: 1, 5, 2, 6, 3, 7, 4. This 

 is probably largely due to the greater number of spores used by the 

 more successful methods. All will give good results when the 

 relative number of spores used is considered. 



With all these different methods of applying spores and moisture, 

 it is essential to supply all the water possible without having it 

 form large drops and run off. 



As a supplement to the local moistening, it is necessary to keep 

 the inoculated plant in a moist chamber for 12 to 24 hours. In the 

 experiments by the writer and his associates the preferred method 

 has been to keep the plant in the moist chamber 48 hours. 



The matter of a proper moist chamber is a problem of considerable 

 moment. Glass bell jars are good, but costly and easily broken. 

 A tightly closed wooden and glass chamber of considerable size was 



