Infrageneric Classification
The genus Cyathus was first subdivided into two infrageneric groups (i.e., grouping species below the rank of genus) by the Tulasne brothers; the "eucyathus" group had fruit bodies with inner surfaces folded into pleats (plications), while the "olla" group lacked plications. Later (1906), Lloyd published a different concept of infrageneric grouping in Cyathus, describing five groups, two in the eucyathus group and five in the olla group.
In the 1970s, Brodie, in his monograph on bird's nest fungi, separated the genus Cyathus into seven related groups based on a number of taxonomic characteristics, including the presence or absence of plications, the structure of the peridioles, the color of the fruit bodies, and the nature of the hairs on the outer peridium:
Olla group: Species with a tomentum having fine flattened-down hairs, and no plications.
- C. olla, C. africanus, C. badius, C. canna, C. colensoi, C. confusus, C. earlei, C. hookeri, C. microsporus, C. minimus, C. pygmaeus
Pallidus group: Species with conspicuous, long, downward-pointing hairs, and a smooth (non-plicate) inner peridium.
- C. pallidus, C. julietae
Triplex group: Species with mostly dark-colored peridia, and a silvery white inner surface.
- C. triplex, C. setosus, C. sinensis
Gracilis group: Species with tomentum hairs clumped into tufts or mounds.
- C. gracilis, C. intermedius, C. crassimurus, C. elmeri
Stercoreus group: Species with non-plicate peridia, shaggy or wooly outer peridium walls, and dark to black peridioles.
- C. stercoreus, C. pictus, C. fimicola
Poeppigii group: Species with plicate internal peridial walls, hairy to shaggy outer walls, dark to black peridioles, and large, roughly spherical or ellipsoidal spores.
- C. poeppigii, C. crispus, C. limbatus, C. gayanus, C. costatus, C. cheliensis, C. olivaceo-brunneus
Striatus group: Species with plicate internal peridia, hairy to shaggy outer peridia, and mostly elliptical spores.
- C. striatus, C. annulatus, C. berkeleyanus, C. bulleri, C. chevalieri, C. ellipsoideus, C. helenae, C. montagnei, C. nigro-albus, C. novae-zeelandiae, C. pullus, C. rudis
Read more about this topic: Cyathus