220 



THE ASCOMYCETES 



*nose fungi usually become uniseptate as an initial step in germina- 

 tion. At the apex of the germ tube, moreover, a thick-walled, 

 dark organ of attachment, called an appressorium, develops. The 

 appressoria anchor the organism during host penetration. Ap- 

 pressoria are developed in culture and on the host in Glomerella 

 but have never been observed in Gnomonia. 



A few of the best-known members of this family include 

 Gnomo7iia erythrostoma on cherry [Brooks (1910)], G. lep- 



FiG. 85. . Diaporthe chri. A. Pycnidial stage (diagrammatic) of Fhomopsis 

 citri, in section, bearing two kinds of spores, oval ones that germinate and 

 thread-like ones, stylospores or scolecospores, that have not been found 

 capable of germination. B. Conidia. C. Stylospores. D. Germinating 

 conidia. E. Diagram of perithecial stroma in section bearing long-beaked 

 perithecia. F. Ascus with thickened apex. G. Germinating ascospores. 



tostyla on w^alnut, G. veneta on sycamore [Klebahn (1905, 1918), 

 Edgerton (1908)], G. iilmea on elms [iMiles (1921), Pomerleau 

 (1938)], Glomerella cingiilata on apple [von Schrenck and 

 Spaulding (1903), Shear and Wood (1913)], G. gossypii on 

 cotton, G. lagenaria on melons, G. Undeumthimia on beans, and 

 G. glycines on soybeans. 



Details of perithecial development among the species just men- 

 tioned are best known for Giwmonia erythrostoma. Brooks 

 (1910) observed that this organism possesses filamentous sper- 

 matia, borne in pycnidia, W'hich he deemed functionless. Asco- 

 gones bearing trichogynes are also formed, but the trichogynes 



