E. S. Salmon and H. Wormald 11 



Mar. 25. A single tendril of typical conidia was found at 2 mm. from the point 

 of inoculation. 



Jan. 25, 1916. Distinct sunken canker 2 cm. long and one-third round the 

 branch. 



No. 2. (Branch 0-8 cm. diam.) 



Jan. 15, 1915. No change to be observed. 



Feb. 16. The bark was discoloured for 2-3 mm. round the wound; at 4 mm. 

 from the point of inoculation was a small group of pustules. 



Mar. 3. A tendril was observed projecting from one of the pustules; it was 

 removed and microscopic examination showed conidia as before. 



Jan. 25, 1916. The affected area, now 2 cm. long and extending three-quarters 

 round the branch, was only slightly depressed below the general surface but was 

 distinguished from the rest by its darker colour. 



Feb. 24. Branch dead above the canker, as shown by absence of any growth, 

 the rest bearing leaves and young fruit. 



No. 3. (Branch 1 cm. diam.) 



Jan. 15, 1915. No external change. 



Feb. 16. No canker and no discoloration noticeable but round the wound was 

 an irregular cii'cle (about 1 cm. diam.) of tendrils. 



Jan. 25, 1916. The affected area appeared as a sUghtly sunken canker 2 cm. 

 long and extending half-way round the branch. 



Thus in the two series of experiments eight inoculations through 

 wounds were made in all, and in every case not only was there a "canker" 

 formed round the point of inoculation but the fruiting fungus appeared 

 in the affected tissues and produced tendrils of conidia resembling those 

 found on "cankers" arising froni natural infections. Since "cankers" 

 were so readily induced when the fungus, either in the form of conidia 

 or of mycelium, was introduced into the internal tissues through wounds, 

 the negative results in those cases in which conidia were applied to the 

 uninjured bark indicate that in all probability the fungus is solely a 

 wound-parasite. 



Preventive Measures. 



From our knowledge of the biology of the parasite, it is very unhkely 

 that spraying with any fungicides will hold the disease in check. The 

 direct measures should consist of a search for all "cankers," and the 

 cutting of them out, down to the sound tissues, at a time when the 

 disease is dormant ; it will be advisable to paint over the wounds made 

 with Stockholm tar. All dead branches must be cut out and froni'pily 

 hurned, as otherwise the fungus producing conidia on the dead wood 

 might constitute a dangerous source of infection. The indirect measures 



