WHITE-PINE BLISTER RUST. 17 
as the safest place for such work at that time. In midsummer, 1916, 
before the disease was fairly started on the bushes on the island, it 
was found to be pretty generally distributed over New England on 
Ribes, having plainly been widely disseminated there before the 
Block Island experiment was started. Conditions on the island are 
not very favorable for Ribes and are decidedly unfavorable for white 
pines. Pinus nigra var. austriaca is the only pine seen on the island, 
and it occurs only in protected hollows. 
Table I presents the general results of tests made in the green- 
house where inoculations were made with both asciospores and 
urediniospores. A preliminary statement has been published, giv- 
ing the earlier results of this work (147). This table is to be inter- 
preted as follows: 
In the columns headed "Susceptibility," a single cross (X) means slight infection, 
two crosses (XX) mean a medium degree of infection, and three crosses (XXX) mean 
heavy infection. 
There are no means of knowing what degree of susceptibility was indicated by 
the experiments of European and Canadian investigators, whose results are included 
in section 1 of Table I. The foreign experimenters are first listed alphabetically 
under each species of Ribes, then the work done in this country is given in a similar 
manner. The varietal tests (sections 2 to 4 of Table I) are wholly the work of the 
Office of Investigations in Forest Pathology, there being practically no data in 
foreign literature on inoculations of horticultural varieties. 
In numerous cases but a single test has been made as yet; but the 
general behavior of the tested plants in the spread of the fungus, 
the type of its fruiting, etc., during the rest of the season are con- 
sidered in the final estimate of susceptibility. When a single test 
has been made under favorable conditions, it is believed that the 
results are fairly indicative of the susceptibility of the species or 
variety tested. Many tests were made under conditions known to 
be adverse, and the negative results are largely due to this cause alone. 
But these tests are given with the others to give some idea of what 
has been done. Scanty numbers of tests are often due to the Ribes 
stock dying before a second test could be made. This is true of 
many cuttings which made a weak start and did not survive potting. 
In sections 2 to 4 of Table I, relating to the varieties of Ribes, an 
attempt has been made to use varietal names that are intelligible to 
horticulturists as accepted by the American Pomological Society. 
Acknowledgment is made to the Office of Horticultural and Pomo- 
logical Investigations of the United States Department of Agriculture 
for help in this matter. In some cases varietal names are given 
which are considered to be synonyms of others in the list; but in such 
cases the stocks used under the two names were evidently different. 
Varieties and even species of Ribes supplied by nurserymen are often 
other than what they purport to be, and in some cases they are 
mixtures of two or more distinct things; hence, the varietal names can 
not be taken as being absolutely reliable. 
46103°— 21— Bull. 957 2 
