8 Fig " Canker,'' caused hy Phoma cinerescens Sacc. 



(1) A V-shaped cut was made through the bark of a branch of one 

 of the young fig-trees ; the triangular tongue of bark was turned back 

 and a little agar bearing mycelium was removed from the plate culture 

 and inserted between the bark and the wood. The free portion of bark 

 was then pressed back into its place and the wound was covered up 

 with cotton wool and tinfoil to prevent possible infection from air-borne 

 spores. This precaution was perhaps unnecessary for as shown in 

 Exp. II exposed wounds remained uninfected. 



(2) From another branch a small portion of the bark (about 1 cm. x 

 0-5 cm.) was entirely cut away and agar with mycelium placed on the 

 exposed tissues, after which the wound was bound up as in the previous 

 case. 



On September 16 the coverings were removed and the following 

 results observed : 



(1) Round the inoculated wound was a depressed very dark elliptical 

 portion of bark 2-5 x 1-2 cm. ; the tissue bordering the canker was pale 

 in colour and thus showed strong contrast with the sunken canker. 

 The latter bore a few pycnidia which appeared on the surface as small 

 protuberances with incipient "tendrils" consisting of conidia which 

 on microscopic examination were indistinguishable from those obtained 

 from natural cankers. 



(2) The result of the second inoculation was similar to the one just 

 described except that the canker was smaller, its dimensions being 

 1-8 X 0-8 cm. ; tendrils with typical conidia were again produced. 



In both cases the infected branch was seen in September 1914 to 

 be sHghtly swollen when viewed in a direction perpendicular to the 

 surface of the canker. No further increase in the size of these cankers 

 was subsequently observed and in the following season both branches 

 bore fruit and leaves. In February of the present year (1916) leaves 

 and fruit again appeared but by the middle of March the secondary 

 branch immediately above the canker of the second inoculation, and 

 on the same side of the main branch as the canker itself, showed signs 

 of wilting for the leaves began to droop and turn yellow, indicating 

 that the transpiration current was interrupted in the neighbourhood 

 of the canker. 



Experiment II. Semicylinders of potato were placed in Roux's 

 tubes and sterilized in an autoclave by steaming at a temperature of 

 115° C. for 30 minutes ; they were inoculated from an agar slant culture 

 on June 22, 1914. The fungus grew vigorously on the potato ; pycnidia 

 were readily produced and by July 15 "tendrils" of conidia began to 



