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THE STRUCTURE OF THE ACERVULUS, THE FLOWER CLUSTER OF CHAMAEDOREOID PALMS
Author(s) -
Uhl Natalie W.,
Moore Harold E.
Publication year - 1978
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1978.tb06057.x
Subject(s) - bract , biology , vascular bundle , stamen , botany , apex (geometry) , palm , anatomy , inflorescence , pollen , physics , quantum mechanics
Developmental evidence shows that the acervulus, a distinctive flower cluster found only in the chamaedoreoid group of palms, is a form of cincinnus. In Hyophorbe indica Gaertner, the unit consists of a row of sessile flowers, the upper 3–4, staminate and the basal flower, pistillate. During initiation, each new flower originates from divisions in the T 2 and underlying layers of the lower right or left flank of the apex of the preceding flower. A bract subtending the first flower is evident in early stages, is displaced basipetally as the flowers are formed, but is obscured when flowers are mature. No other bracts are associated with the unit. One to two outer bundles of the vascular cylinder of the rachilla develop first to the uppermost flower. Subsequently, bundles to other flowers arise as lower branches of the first bundle and from other, often small outer bundles of the rachilla that become floral traces or produce one or more branches to a flower. Many of the bundles supplying the flowers bend sharply downward in the cortex of the rachilla, apparently reflecting the basipetal sequence of floral inception.