16 BULLETIN 209, TJ. S. DEPARTMENT OF AGRICULTURE. 
HYBRIDS. 
In the attempts to secure resistants suited to soil, climatic, and 
other conditions which at the same time would prove congenial, 
lasting, and productive stocks on which to graft the Vinifera varie- 
ties, many difficulties were encountered. For instance, the stock 
may be adapted to the soil, but it may be so hard to root as to make 
its commercial use impracticable. Again, the stock may be suited 
to the soil and it may root easily and be resistant, but not congenial 
to or make a lasting junction with Vinifera varieties; or the congeni- 
ality of the variety may be good, but the fruitfulness of the graft 
may be impaired. 
In many cases also no resistant species are exactly suited to the 
soil and climatic conditions. To overcome such difficulties and 
others of like nature, hybrids have been and are being produced, in 
the breeding of which such of the native American species were 
selected as possess the various qualities desired. (See Pis. VIII and 
IX.) In this work some remarkable successes have been achieved, 
such, for instance, as Riparia x Rupestris, No. 101; Riparia X Rupes- 
tris, No. 3306; Riparia X Rupestris, No. 3309; Solonis X Othello, 
No. 1616; Rupestris x Cordifolia, Nos. 107-11; Riparia x (Cordi- 
folia X Rupestris), Nos. 106-8; Rupestris X Berlandieri, No. 301 A; 
Bciiandieri x Riparia, No. 420A; and Monticola X Riparia, No. 
18808. 
Efforts have also been made to produce hybrids between the 
Vinifera and American native-grape varieties which would be resist- 
ant to phylloxera and at the same time give satisfactory crops of 
fruit of desirable character and quality. (See PI. X, fig. 2.) By 
having such direct producers, the cost of grafting would not only be 
avoided, but congeniality would not have to be reckoned with. Some 
remarkable strides are being made along this line. A number of 
these hybrids are under test in the experiment vineyards, but so far 
it is not possible to say that any of them are better than or equal to 
some of our finer varieties of native American grapes or that they 
have as good phylloxera-resistant qualities. 
GROWTH RATINGS OF RESISTANT VINES AND DIRECT PRODUCERS. 
In Table IV the upper numbers after each name in the columns 
headed " Experiment vineyard" show the years when the vines were 
planted; the lower numbers show the growth ratings, which in all 
cases were made in the autumn of 1913. 
The growth or adaptability of each variety at each vineyard where 
it is under test is expressed in the form of a percentage rating on a 
scale in which the growth of the variety under conditions for which it 
is well adapted is taken as the standard of excellence, 100 per cent. 
