BULLETIN 197. 



GRAPE CULTURE IN CALIFORNIA. 



141 



FIG. 4. Rupestris Metallica of South Africa. 



Rupestris Metallica (Fig. 

 . The best varieties of 



Riparia and Rupestris give 



excellent results when they 



grow under appropriate soil 



and climatic conditions. 



Their range of adaptation, 



however, is comparatively 



small that is, they are likely 



to .give unsatisfactory results 



when planted in locations 



which differ in any consider- 

 able degree from those which 



suit them best. This seems 



to be due in great part to the 



direction their roots naturally 



take. Roots of Riparia are 



for the most part spreading 



and superficial, and succeed only where sufficient moisture exists near 



the surface. Roots of Rupestris are, on the contrary, plunging and 



deeply penetrating, and fail if an impenetrable subsoil prevents their 



taking their natural posi- 

 tion. 



Experience has shown 

 that crosses between 

 Riparia and Rupestris 

 have a much wider range 

 of adaptation than either 

 of their parents, owing 

 to the fact that they are 

 capable of forming a 

 strong root system in 

 both the upper and lower 

 layers of the soil. More- 

 over, the best of them 

 retain all the good quali- 

 ties of both parents 

 high resistance to Phyl- 

 loxera, ease of rooting 

 and grafting, vigor and 

 fruitfulness of grafts. 

 The best of these hybrids, 

 according to European 



FIG. 5. Riparia x Rupestris 3309. One half natural size. 



