DASYSCYPHA. 



271 



Dasyscypha (Peziza) Willkommii, Hartig.^ The Larch Canker 

 (Britain and U.S. America). Everywhere in the mountains, the 

 home of the larch, one finds, on young branches and old stems, 

 depressed canker-spots, on which the sporocarps of Dasyscypha 

 Willkommii are developed. Young twigs, when attacked, are 

 already conspicuous in .July and August by their pale and 

 withered needles, and on them small 

 canker-spots will be found ; these rapidly 

 enlarge so that on older stems they may 

 reach very great dimensions. Hartig easily 

 succeeded in producing canker-spots on 

 healthy trees by artificial infection. 



If canker-spots are examined soon after 

 the death of the bark, the stromata will 

 be found as yellowish -white pustules. 

 Conidia are produced either on the free 

 surface or in the internal cavities of a 

 stroma; they are tiny unicellular hyaline 

 bodies, produced from little conidiophores. 

 Hartig never succeeded in getting these 

 spores to germinate. If the atmosphere 

 be moist enough the apothecia make their 

 appearance later on the same places ; they 

 are externally yellow, and internally orange- 

 coloured. The apothecial disc carries long 

 thread-like paraphyses and cylindrical asci 

 with rounded apices (Fig. 143). The asco- 

 spores are oval, unicellular, and hyaline. They germinate and 

 give off one or two germ-tubes which are unable to penetrate 

 the periderm of a host-plant, and only find entrance through 

 wounded places. Wounds are very common on larch as the 

 result of hail, or injury to twigs by snow or ice, or destruction of 

 needles by insects. For example, the Larch-moth {Coleophora 

 laricella) is well known to cause less damage on the mountains 

 than in the lower regions, and in the same degree Dasyscypha is 

 least injurious to mountain forests. 



The mycelium is septate and much branched ; it spreads 

 chiefly through the soft bast, especially in the sieve-tubes and 



Pio. 



143. — Dasyscyplta 

 Willkommii. Three asci and 

 two paraphyses isolated 

 from an apothecium. (After 

 E. Hartig.) 



^R. Hartig, Untermch. axis d. forsthotan. Institut Munchen, i., 1880. M. Will- 

 komm, Mikros. Feinde des Waldes, ii., 1868. 



