1912-1913-] Notes on Parasitic Ascomycetes. — III. 29 



to bear considerable resemblance to a Puccinia in habit. As 

 the specific name implies, each ascus contains only four spores ; 

 and these are brown, and divided near the lower end by a cross 

 septum into two very unequal cells. 



An allied species, named Phacidium infest ans Karst, is 

 rare in Britain, but reported to be very destructive to fir-trees 

 in Finland. It attacks the living leaves, and forms small, 

 rounded, blackish spots. When the ascophore is ripe, the 

 affected epiderm of the leaf splits from the centre into several 

 teeth, and exposes the pale disc in which the asci are em- 

 bedded. Each ascus contains eight spindle-shaped spores. 



Living leaves and stems of Sneezewort (Achillea Ptarmica) 

 are sometimes attacked by Schizothyrium ftarmicaz Desm., a 

 parasitic fungus allied to Phacidium. It produces small, 

 rounded, or elliptical black spots, which are often very 

 numerous on the leaves, especially when the host-plant is 

 severely attacked and stunted in growth by the parasite. In 

 the early or pycnidial condition, known as L&ptothyrium 

 ptarmicai Desm., the spots are almost plane, and contain 

 ovate-oblong sporidia ; but as the spots ripen they become 

 more convex, and finally open by a longitudinal or stellately 

 radiating slit. The number of spores in each ascus is variable, 

 being sometimes eight and sometimes only two. 



Another parasite belonging to the same group occurs not 

 unfrequently on the leaves and stems of Self-heal (Prunella 

 vulgaris). Black spots are produced on the upper surface of 

 the leaves. These consist of fascicles of encrusting fibrils 

 which radiate outwards from a central tubercle. This was 

 formerly regarded as an independent species, and described 

 under the name of Asteroma prunellw Purt. ; but specimens 

 obtained by myself in various parts of the West of Scotland 

 have shown the Asteroma to be merely an immature form of 

 a parasitic Discomycete, which has been described under the 

 name of Ephelina prunellai Phil. In its fully matured con- 

 dition, the thickened central portion becomes a stroma on 

 which are developed small groups of blackish-brown asco- 

 phores. The asci contain hyaline, undivided spores, which 

 are oblong, and either straight or slightly bent. 1 



1 See 'Transactions of the British Mycological Society,' vol. iii. p. 114; 

 Plate 6, figs. 2, a, b, c, d, e, f. 



