A foundation monograph of Ipomoea (Convolvulaceae) in the New World

Inflorescence
Most inflorescences consist of cymes that arise from the leaf axils. Cymes are nearly always solitary but are very variable in the number of flowers. In many species the cymes are reduced to a single flower while in others the cymes may be compounded with up to 15 or more flowers. The number of flowers in the cyme is often a useful although somewhat imprecise taxonomic character.
Not all inflorescences are obviously cymose in structure, some are more or less corymbose (especially in the Quamoclit Clade) or racemose (e.g. Ipomoea bombycina, I. reticulata, I. corymbosa) or umbellate (some forms of I. batatas), even appearing paniculate in some forms of I. lineolata or I. philomega. In quite a few species, the pedicels are very short so the inflorescence is subcapitate in form. In the Arborescens Clade and also in a number of woody lianas, the inflorescence arises on short leafy (bracteate) branchlets with no obvious cymose structure.
Bracts and bracteoles
We have generally avoided using the term bract since in most twining or trailing species, the bracts are not clearly differentiated from the leaves, the cymes arising in the axils of the leaves which function as bracts. In the erect species and also in some or the arborescent species where the inflorescence is either terminal or borne on small branchlets bracts are more clearly differentiated from leaves, typically smaller and narrower and diminishing in size towards the branch tips and, in this situation, we have used the term bract. Some authors, however, use the term bract for the very different structures that arise at the inflorescence branching points or at the base of the pedicel in unbranched inflorescences. We refer to these as bracteoles, only rarely differentiating between primary bracteoles (at the first branching point) or secondary bracteoles (at the higher branching points) as these rarely differ in any significant way. In many species the bracteoles are inconspicuous and caducous (and have never been observed in a few species), but in others they are prominent and persistent, especially in the Pharbitis Clade, and occasionally even forming an involucre around the flowers where the pedicels are very short, notably in I. neurocephala and I. involucrata.
In the majority of species the bracteoles are small (< 3 mm long), often linear, lanceolate or scale-like and caducous. In a few species, Ipomoea blanchetii is an example, we have not observed bracteoles in any specimen available to us. In others, they are relatively persistent, particularly in species, with a subcapitate inflorescence. These include I. indica, I. villifera, I. mairetii, I. argentinica, I. asplundii, I. chrysocalyx, I. racemosa, I. amazonica, I. eriocalyx, I. setifera, I. fimbriosepala, I. burchellii, I. pohlii and I. mcvaughii. In a very few species the bracteoles are expanded, persistent and form an involucre around the inflorescence as in I. neurocephala, I. involucrata, I. bracteata and I. suffulta.