WHITE-PINE BLISTER RUST. 23 
Recently Thayer (159) and Bunyard (8) have published results 
of their studies of the cultivated red and white currants. They find 
these currants to be of mixed and badly confused parentage, but con- 
clude that certain varieties sprang from each of the three species, 
Ribes vulgare, R. rubrum, and R. petraeum. Many varieties are still 
to be assigned to the proper species ; hence, they are grouped in Table I 
under the name R. vulgare, for convenience, as it is yet impossible 
to assign all of them to any species. 
The gooseberries are well known to be in many cases a mixture 
of Ribes reclinatum with several American species or even pure selec- 
tions of American species. For convenience they are grouped under 
the species name, R. reclinatum. 
Susceptibility of Ribes Species and Varieties to Cronartium ribicoia. 
Estimates of the susceptibility of the various species and varieties 
of Ribes have been made. (See Table I.) These are based on work 
done in the greenhouse and on results of the experiments out of doors 
on Block Island. These f estimates have been made mostly by two 
persons, so that they are believed to be quite reliable and accurate 
by the standards chosen. The estimates for the inside experiments 
were made entirely independent of those out of doors. The two 
agree surprisingly. They are based on the results of work covering 
several years, but many of the species and varieties have been sub- 
jected to infection but a single year. A few species will be noted 
which have remained immune in our tests. But some of these 
species are known to have become infected elsewhere. This is true 
of Ribes alpinum which is reported to take this disease in Europe, 
although it is entirely resistant in North America (35, 53). Ribes 
innominatum has been well tested and took the disease only on newly 
developed leaves. It is a very resistant species. Ribes sterilis, R. 
tenue and R. villosum have not yet undergone satisfactory tests, so 
that no conclusive statement concerning them can be made. 
The species of Ribes vary in susceptibility from the extremely 
susceptible Ribes nigrum to the very resistant R. leptanthum. On 
the former are produced the maximum number of uredinia and telia 
of the largest size, while on the latter the minimum number is pro- 
duced and these are poorly developed. Ribes alpinum has been 
entirely immune with us, although it takes the disease in Europe. 
The varieties of a cultivated species run fairly true to the species 
as a whole. Some real variation among varieties is believed to depend 
upon their mixed parentage. Many tests were necessarily made when 
the plants were not at the most favorable stage of development for 
the fungus to attack, and it is likely that further tests of aberrant 
varieties may bring most of them back into agreement with the species 
to which they belong. Of the varieties of the cultivated red currants 
