A Grammatical Dictionary of Botanical Latin

Subsection, a subdivisional rank above species; subsectio,-onis (s.f.III), abl.sg. subsectione; the epithet in the name of a subsection or lower subdivision of a genus is preferably a plural adjective (Article 21.3); see subgeneric epithets;

  subsectio,-onis (s.f.III): 
        sg.             pl.
Nom. subsectio     subsectiones
Gen. subsectionis  subsectionum
Dat. subsectioni   subsectionibus
Acc. subsectionem  subsectiones
Abl. subsectione   subsectionibus

The PLURAL adjective should agree in GENDER with the generic name. Gender refers to masculine, feminine and neuter. The plural adjective is the recommended word form for ranks below subgenus and below section and is thus recommended for the rank of subsection, series and subseries (Article 21.2).

NOTE: All legitimate Latin or Latinized adjectives may be used as subgeneric epithets whether or not they are used as species epithets.

- ad subsectionem Esculentos sepalis superioribus persistentibus pertinens, belonging to the subsection Esculenti by the persistent upper sepals.

- subsectio nova a subsectione Laxiglumis distincta, new subsection distinct from the subsection Laxiglumi.

NOTE: a noun used to describe another, and denoting the same person or thing, agrees with it in case: e.g. above: subsectione (abl.) and Laxiglumis (abl.) even though one is a singular and the other a plural noun.

Hypothetical examples might include genus Cyperus, subsection Rotundi, subsection Refracti, subsection Lancastrienses, subsection Filiculmes, subsection Sphaerici.