42 DISEASES OF CROP-PLANTS 



Without doubt many or most of the Fungi Imperfecti have 

 affinities with ascomycetes or basidiomycetes, but it is probable 

 that in a large number of cases the " higher " form, of fructifica- 

 tion has fallen into disuse, and in others is produced only ex- 

 ceptionally. 



Three orders are used in the current system of classification. 

 These are divided into families, and within the families a mainly 

 artificial method of grouping according to coloration and the 

 number of divisions in the spores is adopted. 



1. Sphceropsidales. 



This order consists of forms in which the conidia are produced 

 typically on short, closely-set conidiophores in enclosed spherical 

 or flask-shaped fruiting bodies (pycnidia) opening by a pore or 

 slit and resembling the perithecia of ascomycetes. In the 

 family Sphcerioidaceae, which contains those with black or dark 

 brown, often leathery or carbonaceous pycnidia, are a great 

 many kinds which occur on dead or failing leaves, fruits, and twigs, 

 and some which are definitely parasitic on similar material. To 

 this family belong Phyllosticta and Phoma, of which a very large 

 number of species have been described as occurring in leaf-spots 

 or in the cortical tissues of stems. Here also belong Diplodia, 

 which is elsewhere discussed, Phomopsis, Cytospora, Sphaeropsis, 

 and the large genus of leaf-spot fungi Septoria. 



2. Melanconiales. 



In this order of only one family, Melanconiacese, the layer of 

 short conidiophores is not enclosed in a regular pycnidium, but 

 occurs in groups or patches (acervuli) which are usually irregu- 

 larly enclosed at first, often only by the epidermis, and become 

 exposed sooner or later. It includes Gloeosporium and Colleto- 

 trichum, the fungi of the anthracnoses (see page 22), Melan- 

 conium (see sugar-cane), Septogloeum (ground nut), and Pes- 

 talozzia (coconut). 



3. Moniliales (or Hyphomycetes). 



This is an order of great diversity distinguished as a whole 

 only by the free-standing dissociated conidiophores or conidia- 

 forming hyphai. The forms of these range from hyphae which 

 divide up without much differentiation into conidia to special 

 conidiophores of peculiar structure or with elaborate branch- 

 systems. There are four families. The Moniliaceae (or Mucedi- 

 naceae) and the Dematiaceae contain the forms in which the 

 hyphae associated with reproduction are not more than loosely 

 aggregated ; the former contains the hyaline or brightly coloured 

 kinds, the latter those with either hyphae or conidia, or both, 

 dark coloured, mostly smoky brown or black. In the Moniliaceae 



