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.
Leaf Arrangement
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 (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.
