BULLETIN 197. GRAPE CULTURE IN CALIFORNIA. 153 



This is substantially the explanation given of the dying of vines in 

 Santa Clara, in Bulletin 134, which was published before the region 

 was declared infested by Anaheim disease. Whether this explanation 

 is sufficient is still doubtful, though it is rendered probable by the 

 fact that healthy young vineyards are now growing in Santa Clara, 

 on the same soil where vines have been killed by ' ' Anaheim disease. ' ' 



FK;. 17. Bluck Knot on arm of old vine. 



Black Knot. This is one of the commonest and most widely dis- 

 tributed diseases of the vine in California. Many specimens are received 

 by the Experiment Station every year, from nearly all vine -growing 

 sections. It consists of peculiar growths, or swellings, usually near the 

 surface of the ground on the upper parts of the roots or the lower part 

 of the trunk. It often occurs, also, on all parts of the trunk and 

 branches, but only rarely on the canes. 



As a rule it does little damage unless it occurs on young vines, 

 or attacks old vines very severely. Figure 16 is the photograph of 



