Northern Ontario Plant Database
Leaf Attachments and Arrangements
- node - the point of leaf attachment to a stem.
- internode - the region of the stem between leaves.
- petiolate - a leaf attached to the stem by a petiole.
- sessile - a leaf whose blade is attached directly to the stem, lacking a petiole.
- clasping (or amplexicaul) - a sessile leaf with free bases partly or entirely surrounding the stem.
- sheathing - with a tubular portion of the leaf blade surrounding the stem below the base.
- decurrent - with leaf blade extended downward along the stem, forming vertical lines along the stem.
- ochreate - with stipules forming a thin tube around the stem above petiole.
- perfoliate - with the bases of a single leaf fused around the stem, which appear to go through the leaf blade.
- connate-perfoliate - with bases of opposite leaves fused around the stem, which appear to go through the leaf.
- phyllotaxy - the arrangement of leaves on an axis.
- 2-ranked - arranged in 2 rows, one on either side of the stem or central axis.
- alternate - an arrangement with 1 leaf attached at each node.
- distichous - 2-ranked, with alternate leaves arranged on opposite sides of a stem, not spirally arranged.
- equitant - 2-ranked basal leaves, folded and flattened in the same plane, and with alternately overlapping bases. New leaves emerge between the bases of the previous leaf, e.g., characteristic of irises (Iridaceae), Tofieldia (Tofieldiaceae), and Zingiberales.
- opposite - an arrangement with 2 leaves attached at each node, on opposite sides of the stem.
- decussate - with opposite leaves attached at right angles to the adjacent pairs of leaves.
- whorled - an arrangement with 3 or > leaves attached at each node.
- imbricate - with overlapping bases, the previous layer of leaves or scales overlapping younger layers.
- fascicle - 2 or > leaves grouped in a bundle and bound together at the base, derived from a reduced shoot.
- basal leaves - leaves arranged around the base of a stem.
- rosette - a group of basal leaves.
- cauline (or radical) leaves - leaves arranged along an aerial stem.
- vernation - the arrangement of leaves in a bud.
- circinate - a coiled vernation, with the frond apex in the centre of the coil; produced the distinctive fiddlehead-shaped young leaves in ferns.
arrangement of stomates (pores in leaf epidermis, surrounded by guard cells and subsidiary cells).
- anomocytic - with no specialized subsidiary cells.
- paracytic - with 2 specialized subsidiary cells surrounding the guard cells.
- paratetracytic - with 4 specialized subsidiary cells surrounding the guard cells.
- pericytic - with 1 specialized subsidiary cell surrounding the guard cells.
- amphiparacytic - with 2 rows of 2 subsidiary cells surrounding the guard cells.