596 



(r) also forms corresponding^ excrescences and. in places, develops thick 



bark scales. 



In the canker of the cherry, as in all canker diseases, only scattered 



individuals are found diseased in large plantations. I often found in the 



healthy shoots of these cankered examples 

 abnormally broadened medullary rays, a ])he- 

 nomenon which may be observed also in 

 other kinds of trees. I. therefore, surmise 

 that the inclination to become diseased i^'itli 

 canker may he found in the indii'idnal ten- 

 dency tozuard a zi'idcnin;! of the medullary 

 rays. 



Thk C'ankkk (Scab) of thk Gkapkvine. 



In the older wood of grapevines near 

 the surface of the soil, about lo to 30 cm. 

 abo\e it. are found scattered, small spherical 

 or large barrel-shaped, out-pushings of the 

 wood from the bark, with a beadv. irregular 

 upper surface, split lengthwise into fibres. 

 Fig. 140 shows a beady canker swelling 

 between the strips of bark which are drawn 

 in white. In small, isolated outgrowths, their 

 production, according to (jothe's^ investiga- 

 tions, is clearly recognizable as the over- 

 growth tissue of longitudinal clefts. The 

 clefts a])pear at the cdi::,c of the annual ring, 

 from which it must be concluded that they 

 were produced at the time when the de- 

 \elopment of the next annual ring began, 

 caused b}- the d}ing back in spots in the 

 cambial zone in the spring. In regard to the 

 production of the excrescences, I have stated 

 some dififering observations of my own, 

 under the head of the disease to be treated 

 next. — Canker of the Spirea. 



The injury, which killed the cambium. 

 has also caused a considerable circular sur- 

 face on the old wood to turn a deei) brown. 

 The overgrowth beginning at the healthy 

 place, which often ciuickly closes the cleft, is characterized by an excrescent 

 luxuriance of the wood and bark. The woody edges, curling out towards 

 one another, consist of soft, ductless parenchyma wood, without any real 



Flsf. 140. clunker excrescences 

 in the graj)evinc. 



1 Mitteilungen liber den schwarzen Bienner und den Grind der Reben. 

 und Leipzig, H. Voigt, 1878, p. 28 ft. 



