414 



Jounxal of Agriculture, Victorm. [10 July, 1917. 



before (the details of its action were scientifically explained. In the last- 

 named ai-ticle these authors, after describing the manner in which the 

 slender mycelium of the fungus in the deeper tissues gradually con- 

 denses near the surface to form sclerotia, describe the mode of action 

 of tiie corrosive swab. The following is an abridged translation : — 



The fungus only assumes the sclerotium form late in the season; it is seldom 

 to be found in tissues attaclced earlier. Sclerotia are sometimes to be found 

 among barli fragments, but tbey are generallv small. They are more developed 

 on the edge of the scar, where they form a black zone. A section clearly shows 

 the different stages of development; the smallest sclerotia are usually the 

 fvirthest from the centre; these, often composed of only two or three irregular 

 cells witli brown walls, are situated between the epidermus and the cuticle 

 (Fig. 7). The sclerotia continue to grow, and until they become large they are 

 sheltered from external agents by the cuticle, and it is easy to understand that, 

 under these conditions, iron sulphate solution may be harmless to them. When 



r 







Fig. 13. 



Section of portion of a scar in early spring of the season following 

 its development, showing internal fissures, as at B ; a sclerotium is 

 shown at A which is sprouting at a, a; C, fibre-bundle of bark; U, 

 tissue containing abundant mycelium of the fungus (x 100). After 

 Viala and Pacottet. 



they have grown larger they tear the cuticle (Fig. 8), and after a while become 

 entirely exposed. They are also formed more deeply in the epidermis, and 

 even in the tissues of the bark. Their tliickness is then considerable, and the 

 total destruction of the mycelium by swabbings becomes difficult (Fig. 9). 



Sclerotia remain dormant all the winter. In spring, even at low temperature, 

 development commences, as may be seen eitlier on the vine or in the laboratory. 

 It readily takes jdace on detached canes placed in the incubator in a moist 

 atmosphere. At fairly low temperatures, in a cellar for example, they can 

 develop and form spores. Thus is explained the earliness of the disease in 

 spring. Our observations were made at 25 deg. C. I 



