10 July, 1917. J A iith/nrnoxt or lihuk Spot of tht Vine. 



411 



cane becomes woody, the developineut of the fungus is much flower ; 

 nevertheless it sometimes continues to develop for several years in and 

 around the scars first formed, and thus the wood older than one year 

 mav remain a source of infection. 



Shortly after the scar has become distinctly formed sporulation takes 

 place towards its centre which assumes tlie characterii^tic ashy-pink colour 

 (Fig. 6), this continues for a while and then ceases. Hibernating or 

 resting forms then appear. 



As soon as the zone of the pericyclic fibres (the inner bark) is reached, 

 . . . stroma appear on the sunken surface . . . which at once give birth 

 to eoiiidiopliores (spore-bearing filameiits). 



The formation of these ceases about the end of .July, or in August (January 

 or Fel)ruary here). When the wood rijiens, the funi;us continues its vegetative 

 life in tlie tissues, hut conidiophores are no longer produced. Tlicn, at the sur- 

 face of the scar and in the fissures of attacked tissues, the mycelium condenses 

 as sclerotic parenchyma.* 



Before describing these sclerotia, a few other points in connexion 

 with the vegetative stage of the fungus must be considered. The 

 internal mycelium is very slender and difficult to observe, even with 

 a high power microscope, especially in damaged tissues. It is more 

 visible in cells which have quite recently been invaded. 



As we have seen, it is only under certain weather conditions that 

 the fungus can enter the tissues. Moisture in the shape of rain or dew 

 drops is indispeusable. Unlike several other fungi, however, the germi- 

 nation of conidia may take place at a fairly low temperature; hence the 

 possibility of very early invasion. The spread of the fungus is, never- 

 theless, more rapid wlien the weather is both warm and moist. 



'^^^^^^. 



Fig. 7. 



Diagram showing a small sclero- 

 tium of Mangiitia ami}fliita, scl, still 

 covered by cuticle of vine c, cellular 

 tissue of epidermis (bark) e, highly 

 magnified. — After Gouirand and Ber- 

 geron. 



Fig. 8. 



A rather larger sclerotium, becom- 

 ing exposed by the breaking of the 

 cuticle. — After Gouirand and Ber- 

 geron. 



Another important, and to some extent re-assuring point, is the 

 slow spreading nature of this as compared with other vine fungi, such 

 as Oidium and Downy Mildew. This is distinctly stated by several 

 French authors. 



Fortunately this disease has not the galloping and widespread power of dis- 

 semination, and hence, of invasion, of mildew, black rot, or even of Oidium. Its 

 attacks on flowers or young bunches can, no doubt, cause disaster in a vineyard, 

 and exceptionally in a region, but, as a rule, Anthracnose remains localized in a 

 block, or even on a few vines; here, canes, leaves, and bunches are more or less 

 severely damaged ; scars and non-.setting of fruit are the result of its gradual 

 and slow penetration into the tissues. — (F.P., in R. Vit., 8th July, 1015.) 



Viala and Pacottet share a similar opinion — 



An essential character of Anthracnose is its sporadic nature; it is nearly 

 always confined to localized patchcsj whence it spreads progress iveh', but slowlv. 

 — (E. Vit., 14th December, 1905.) •, 



■ ' • Viala & PaiciDttet, E. Vit, 14.12.1905. 



