V] SPHAERIALES 163 



The family is rich in conidial forms, and it is probable that several species 

 of Fungi Imperfecti, including the pycnidial genera Phonta and Hendersonia 

 and also Cercospora, a form with long septate conidia on free conidiophores 

 are stages in the development of members of the Pleosporaceae. 



PLEOSPORACEAE: BIBLIOGRAPHY 



1886 WORONIN, M. Sphaeria Leinatieae, Sordaria fimiseda, Sordaria coprophila, und 

 Arthrobotrys oligospora. Beit, zur Morph. und Phys. der Pilze, iii, p. 325. 



1889 MiYABE KiNGO. On the Life History of Macrosporium parasiticum, Thiim. Ann. 

 Bot. iii, p. I. 



1913 BrierleYjW. B. The Structure and Life History of Zi?//(?jr//?a«naZ^OT««(?i?^(Cohn). 

 Mem. and Proc. Manchester Lit. and Phil. Soc. Ivii, 2, p. i. 



Gnomoniaceae 



The Gnomoniaceae are for the most part saprophytic on the leaves or 

 other parts of plants. The perithecia are embedded in the substratum from 

 which their long necks project. The ascus is characterized by a thickened 

 apex through which a canal allows the exit of the spores. The spores are 

 hyaline and paraphyses are usually not developed. The family differs from 

 the Pleosporaceae in the long neck of the perithecium and the thickened 

 apex of the ascus. There is no stroma, and this fact, as well as the dark 

 colour, distinguishes Gnomonia from the similar genus Polystigma among 

 the Hypocreales. 



Gnomonia erytlirostoma is the cause of an epidemic diseaser known 

 as cherry-leaf-scorch, which attacks the foliage of Primus avium and of 

 several varieties of the cultivated sweet cherry. The mycelium ramifies on 

 the leaf and runs back to the base of the petiole, where it prevents the 

 formation of the absciss layer. In consequence the infected leaves do not 

 fall, but remain hanging on the branches ; they are the only source of 

 infection in the following summer, and their destruction is therefore a sure 

 method of checking the disease. 



Infection usually takes place in June; towards the end of August spermo- 

 gonia appear; they are shallower than those oi Polystigma^ but otherwise 

 very like them, with a wall of closely compacted hyphae and a small circular 

 ostiole opening on the under surface of the leaf. The spermatial hyphae are 

 narrow and tapering, and their extremities are abstricted to form the sper- 

 matia, each of which contains a long threadlike nucleus and a relatively small 

 amount of cytoplasm. 



Soon after the spermogonia have begun to develop certain hyphae near 

 the lower epidermis of the leaf become entwined to form more or less 

 spherical coils, the primordia of the ascocarps. Their apices project in 

 groups of four or five through the stomata, and the terminal cells become 



