WHITE-PINE BLISTER RUST. 41 
METHODS OF INOCULATING KIBES. 
The methods of inoculating liibes 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) When plenty of spore material is available, as is usually the case with aecio- 
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). ) 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 favorite method, 
as it gives good results with reasonable 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 fairly 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 been 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, with 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 
