PARASITIC ROSE CANKER. 



229 



investigation of the rose canker " due to frost " and note that he figures 

 old cankered wood. It would appear that the kind of canker investigated 

 by Sorauer, Laubert, and Kock, and described here are identically the 

 same, only that it depends entirely on the stage of the disease investigated, 

 whether the fungus which is the primary cause, is found or not. Sorauer, 

 himself, failed in the experimental production of the " luxuriierende 

 Uberwallungen " noted in his own specimen. The fungus attack, how- 

 ever, accounts undoubtedly for all the irritations and complications, which 

 later on are certainly increased by the action of frost. 



The observation of my correspondent that the injury is more notice- 

 able during wet weather might be explained by the spongy nature of the 

 parenchyma cells, which readily absorb moisture and thus the growth 

 becomes more pronounced. Another point made by my correspondent — 

 the infective nature of the disease — tends to disprove any such theory as 

 frost injury. 



It remains now to say something concerning the treatment of the 

 injury. A careful watch must be kept on roses for the first signs of the 

 primary spots. Probably one cannot do better than carefully paint these 

 spots and a little of the surroundings as soon as observed with a coat 

 of creosoted wood tar. This would kill the spores and prevent the spread 

 of the disease, and at the same time act as a cover to the wound tissues, 

 should the bark split at any time. If, however, the disease is so far 

 advanced that canker spots are present, I would suggest that they be 

 cut clean out with a sharp knife and then a coating of wood tar or even 

 grafting wax applied. Badly cankered twigs and shoots should be cut 

 away altogether and burnt. 



******** 



A disease of the Blackberry has been investigated which proved to 

 be closely related to the canker of roses. The illustration (fig. 35) shows 

 three large excrescences consisting of parenchymatous cells, and from the 

 investigation of this injury and its history it was evident that the disease 



Fig. 36. — Coniothyriuu tumaefaciexs Guss. 

 a, perithecia ; b, spores. 



on the blackberry and the disease on the rose were identical. The fungus, 

 however, was quite distinct, and it has been found necessary to coin a new 

 specific name for it. The fungus belongs to the same genus as that on 

 the rose, and I propose to name it Coniothyrium tumaefaciens now spec. 

 The other illustration (fig. 36) shows the fruiting bodies of this fungus 

 with some spores, which are magnified to the same degree as those of the 

 rose fungus. The spores are much larger. 



