Forma specialis (plural formae speciales) is a taxonomic grouping allowed by the International Code of Botanical Nomenclature, that is applied to a parasite (most frequently a fungus) which is adapted to a specific host (there being minimal or no morphological differences); this classification may be applied by authors who do not feel that a subspeces or variety name is appropriate. An example is Puccinia graminis.

Forma specialis is abbreviated f. sp.,
formae speciales is abbreviated ff. spp..

See also

• Phytopathology
• Pathovar

References

• International Code of Botanical Nomenclature (Saint Louis Code) (2000). Chapter I. Article 4. Note 3. "In classifying parasites, especially fungi, authors who do not give specific, subspecific, or varietal value to taxa characterized from a physiological standpoint but scarcely or not at all from a morphological standpoint may distinguish within the species special forms (formae speciales) characterized by their adaptation to different hosts, but the nomenclature of special forms is not governed by the provisions of this Code." Access date .