f 



/ 



BENCH-GRAFTING RESISTANT VINES. 



leaves, finds in passing the part where 

 the bark is compressed by the raffia. 

 The large swellings on the two outer 

 vines below the raffia are due to another 

 cause. They are doubtless indicative 

 of disease, and resemble very closely 

 the black-knot which attacks older 

 vines, especially in wet soils. The 

 nature of this disease is not well 

 understood, but as it asually accom- 

 panies an excess of water in the soil it 

 was doubtless due in this case to. heavy 

 rains in late spring after the grafts 

 were planted. 



The accumulation of food material 

 above a constriction of the bark and the 

 consequent starvation of the lower part 

 and root system are similar to what 

 occurs when a vine is girdled. Fig. 

 181 shows an excellent example of this. 

 The vine represented is a Rupestris St. 

 George in the spring after the year it 

 was planted. The first year it made an 

 excellent growth, as evidenced by the 

 roots on the lower part. In the spring 

 of the following year, however, the 

 growth, though at first vigorous, soon 

 stopped and the leaves became yellow. 

 On digging up the vine it represented 

 the appearance shown in the figure. 

 The upper part of the vine had grown 

 to twice the thickness of the previous 

 year down to a point about 4 or 5 

 inches below the surface. Below this 

 point there was no growth at all, and 

 although the roots were still alive they 

 were no larger than the year before. 

 A closer examination revealed the fact 

 that at the point where the change 

 took place the vine had been com- 

 pletely girdled by wire-worms, which 

 had eaten off the bark for about half- 

 an-inch. 



10890. Q 



241 



Figr. 181.- Effect of \Vir 

 Worms on Young- Vine. 



