At this writing, there are seventeen recognized species of Abolboda (Maguire, I.e.), all from Amazonian and northeastern South America.
The four genera are here held together by a community of structural identities.
They commonly have a floral formula that may be expressed 3—3—0 -f
3—3; the petals are all flabellinerved; the anthers are all sagittate; the ovary
is superior; the ovules and seed have small, erect embryos and copious endosperm.
In gross habit a similarity pervades the four genera, the axis being short
and the leaves rosulate in Abolboda, or the stems elongate and leaves rosulate
or imbricate in Orectanthe, or the leaves rosulate-distichous in Xyris, distichous
in Achhjphila. All are marsh herbs, or of sandy areas subject to inundation, or
plants otherwise of wet habitat.
This similarity, identity and concomitance of structure, and prevailing character
of habit and habitat conclusively align the four genera in a single family,
and mutually exclude them from any other monocotyledonous family or families.
Yet generic differences are strong and clear-cut, as evidenced by gross morphology
and histological structure, which together with geographic factors suggest
an ancient phyletic history.
Dr. Carlquist's studies provide evidences that support our taxonomic interpretation
of taxa of the Xyridaceae at both the specific and generic level. Particularly,
his findings on pollen grain structure lend credence to our alignment
of Achlyphila with the other three genera of the Xyridaceae, and provide additional
evidence supporting the separation of Abolboda and Orectanthe. Further,
these studies demonstrate a considerable fundamental structural similarity
among the four genera.
The anatomical structure of the leaves shows a close generic affinity, while
the anatomy of roots, sepals, and petals in varying degrees reveals distinct
generic segregation among the major taxa.