146 PYRENOMYCETES [ch. 



NECTRIACEAE : BIBLIOGRAPHY 



1882 Mayr, H. Ueber den Parasitismus von Nectria cinnabar'ina. Untersuchungen aus 

 der forstbot. Institut zu Miinchen, iii, p. 1. 



1885 Kihlman, O. Zur Entwickelungsoeschichte der Ascomyceten Melanospora para- 

 sitica. Acta Soc. Sci. Fennicae, xiv, p. 313. 



1896 NICHOLS, M. A. The Morphology and Development of certain Pyrenomycetous 

 Fungi. Bot. Gaz. xxii, p. 301. 



1909 Massee, G. On a New Genus of Ascomycetes {Gibsonid). Ann. Bot. xxiii, p. 335. 



1909 Shaver, F. J. Notes on North American Hypocreales. Mycologia, i, p. 41. 



1914 MOREAU, F. Sur le developpement du peVithece chez line Hypocreale le Peckiella 

 laterita, (Fries) Maire, R. Bull. Soc. Bot. de France, Ixi, p. 160. 



Hypocrcaceae 



Polystigma is a small genus, the best-known member of which, P. rubrum 

 develops on the leaves of Pntnus spinosa, of P. insititia and of the cultivated 

 plum, where it produces conspicuous orange, yellow or scarlet stromata. 

 Each of these is the result of a separate infection, and spreads over only a 

 small part of the leaf, so that in autumn, when the leaves are shed, the host 

 is freed from the disease. The fungus, however, hibernates in the fallen leaves, 

 and next spring the ascospores mature, reach the young leaves and there 

 germinate. 



Its development was first studied by Fisch in 1882, and by Frank in 

 1883, and these authors described trichogynes and the union of the latter 

 with spermatia. More recent investigations, however, have shown that these 

 organs, though present, are now no longer functional. 



The germinating ascospore gives rise to a mycelium which ramifies 

 among the cells of the host and forces them apart; the hyphae become 

 massed especially in the intercellular spaces below the stomata, and often 

 push their way to the exterior between the guard cells. Finally the stroma 

 may extend from the upper to the lower epidermis, and only a few isolated 

 cells of the mesophyll remain in the infected region. The hyphae are multi- 

 nucleate, they contain orange pigment and their originally thin walls are 

 modified to form thick gelatinous membranes perforated by fine pits. The 

 gelatinous walls are probabiy utilized as reserve material, for they are partly 

 absorbed during the later stages of development after the fall of the leaf. 



During the summer, large flask-shaped spermogonia appear and open 

 on the underside of the leaf, usually in the position of a stoma. The wall of 

 the spermogonium consists of densely interwoven filaments and it is lined 

 by thin, uninucleate spermatial hyphae (fig. 106). The mature spermatium 

 is a filiform curved structure, narrowed at its free end; it contains a single, 

 much elongated nucleus, staining homogeneously, and occupying the lower 

 half or two-thirds of the cell. All attempts to bring about the germination 



