PYRENOMYCETES 



291 



In Valsa and allies many perithecia, closely packed to- 

 gether, are immersed in the matrix, the beak or ostiolum 

 is elongated, and all the beaks converge and come through 

 the matrix at one point. The common candle-snuff fungus, 

 Xylaria hypoxylon, illustrates the type of vertical stroma 

 so common in this family. The perithecia are immersed 

 in the periphery of the stroma, having their mouths point- 

 ing outwards and opening on the free surface of the stroma. 

 The upper portion of the stroma bears minute, colourless 

 conidia. Daldinia^ not uncommon on dead wood, has a 

 globose stroma about the size of a walnut ; the perithecia 

 as usual are peripheral. The stroma is solid, dark brown, 

 and marked with concentric zones. In Eutype there is a 

 thin, crust-like, black stroma, which sometimes extends for 

 several inches on dead wood or bark. The surface of the 

 stroma is minutely asperate or rough, due to the slightly 

 projecting mouths of the numerous perithecia. The spores 

 are colourless or coloured, one-celled, or divided into two 

 or more cells by the formation of septa. 



larger scale, showing the papilla at the apex, which is perforated for the 

 escape of the spores ; 3, section of perithecium, showing the wall to con- 

 sist of two layers ; 4, an ascus containing eight spores, also two paraphyses ; 

 5, tip of an ascus after treatment with iodine, showing the arrangement 

 for effecting the opening of the ascus, due to expansion of the dark 

 portion, so as to admit of the escape of the spores ; 6, ascospores, one of 

 which is germinating ; 7, brown mycelium with swellings at intervals : 

 this peculiar swelling just below the septum is very characteristic of two 

 or three allied parasitic species of Rosellinia ; 8, a black sclerotium 

 belonging to the fungus, bursting through the cortex of a root, and bear 

 ing several clusters of conidiophores bearing conidia ; 9, a single coni- 

 diophore on a larger scale, showing the mode of branching : conidia are 

 borne at the tips of the branchlets ; 10, free conidia ; n, a pycnidium or 

 second form of conidial fruit, in which the conidia or stylospores are pro- 

 duced in a conceptacle ; 12, stylospores. Fig. i, nat. size ; the remainder 

 highly mag. 



