title: Development of woody branch attachments in Schefflera (Araliaceae or Apiaceae).
abstract: Attachment of branches in Schefflera is unusual in that it involves fingerlike woody extensions that originate in the cortex and pass gradually into the woody cylinder of the parent shoot. We tested the hypothesis that these structures could be roots since Schefflera is a hemi-epiphyte with aerial roots. These branch traces originate by secondary development in the many leaf traces (LTs) of the multilacunar node together with associated accessory traces. In the primary condition, the LTs may be described as cortical bundles. Leaves are long persistent and can maintain a primary stem connection across a broad cylinder of secondary xylem. Under the stimulus of branch development, the LTs form a template for secondary vascular development. Because the LT system is broad, with many traces, the branch attachment is also broad. The fingerlike extensions are attached to the surface of the woody cylinder of the parent stem but are progressively obscured as a continuous cambium is formed. Bark tissues are included within the branch axil because of the extended cortical origin of the initial attachment. The results are discussed in the context of branch-trunk unions in tropical plants, an important component of canopy development.
authors.affiliation: Harvard Forest, Harvard University, Petersham, Massachusetts 01366 USA and The Kampong of the National Tropical Botanical Gardens, 4013 Douglas Road, Coconut Grove, Florida 33133 USA;
authors.forename: P Barry
authors.initials: PB
authors.lastname: Tomlinson
authors.forename: Jack B
authors.initials: JB
authors.lastname: Fisher
authors.forename: Francis
authors.initials: F
authors.lastname: Hallé
authors.forename: Randol
authors.initials: R
authors.lastname: Villalobos