I 



ORDER SPHAEROPSIDALES 577 



stroma; tough leathery to brittle, and dark-colored. The spores often 

 exude from the ostiole in damp weather in a worm-like mass, or cirrhus, 

 consisting of gum and embedded spores. This family contains 359 genera 

 so that it has become necessary to devise some means of subdividing it in 

 a practical and easily applied manner. The scheme most often used was 

 suggested by the great Italian mycologist P. A. Saccardo (1899) and is 

 based on the structure and the color of the spores as follows : 



Amerosporae: spores one-celled, spherical, ovoid or somewhat elongated. 



Hyalosporae: spores hyaline. 



Phaeosporae : spores colored some shade of light brown to black. 

 Didymosporae: spores similar to the foregoing, but two-celled. 



Hyalodidymae: spores hyaline. 



Phaeodidymae: spores colored. 

 Phragmosporae: spores three- or more-celled by transverse septa. 



Hyalophragmiae: spores hyaline. 



Phaeophragmiae: spores colored. 

 Dictyosporae : spores divided by both transverse and longitudinal septa. 



Hyalodictyae : spores hyaline. 



Phaeodictyae: spores colored. 

 Scolecosporae: spores very slender, thread- or worm-like, one-celled to several- 

 celled, hyaline or colored. 

 Helicosporae: spores cylindrical and more or less spirally coiled, one-celled to 



several-celled, hyaline or colored. 

 Staurosporae: spores radiately lobed or star- or cross-shaped, one-celled to 

 several-celled, hyaline or colored. 



This same scheme is used for other orders and families of Imperfect 

 Fungi in which conidia are produced, with the omission of such sub- 

 divisions as are not represented. Where only a few forms are present 

 in the major subdivisions the minor ones based on spore color are often 

 omitted. In the discussion of representative genera of this class the 

 group name, based on the foregoing scheme, follows the generic name in 

 parenthesis. 



The following genera should be mentioned: Phyllostida (Fig. 191A-C), 

 Phoma, Dendro'phoma (Fig. 191D-E) and Macrophoma (all Hyalosporae). 

 Their 2500 or more species are parasitic on leaves and stems of plants. A 

 possible exception is the fungus named by L. R. Fitzgerald (1943) Phoma 

 stenohothri (Holl. & Mor.) Fitzg., which is parasitic upon grasshoppers. 

 The first genus produces leaf spots with definite borders, the others pro- 

 duce less definite spots and occur on other parts of the host as well. 

 Macrophoma, as the genus is usually defined, but incorrectly, according 

 to Petrak and Sydow (1926-1927), has large conidia, over 15 m long, but 

 otherwise is like the others. In these genera the pycnidium is buried in the 

 host tissue but the short ostiole emerges at maturity. The distinctions 

 between these genera are clearly entirely artificial. A leaf spot of the beet 

 (Beta vulgaris L.) is caused by Phyllostida tahifica Prill. The same fungus 



