AFABEGO-Association française des amateurs de bégonias

A little botany: Stipules

Stipules are leaf-like appendages, usually in pairs, at the base of leaf petioles (in dicotyledonous plants).

The leaves of plants in the genus Begonia always have stipules.

Persistence

Persistent

When they are still present at the base of mature leaves, the stipules are called persistent; sometimes they only fall after the corresponding leaves have dropped.

Caducous

Otherwise they are called caducous; they are often early caducous.

    • B. mazae  f. viridis  Ziesenhenne / section Gireoudia / Mexico / persistent stipules
    • B. eminii Warburg / section Tetraphila / Tropical Africa (from Nigeria to Angola) / early caducous, withered stipules

The margin

Entire

The margin is called entire when it has no incisions.

    • B. chlorosticta Sands / section Petermannia / Malaysia (Borneo, Sarawak) / stipules with an entire margin

Dentate

Otherwise it is called dentate.

    • B. auriculata JD Hooker / section Filicibegonia / Gabon / dentate stipules

The persistence and margin of the stipules do not determine which section a plant belongs to.

The shape

Triangular

    • B. mazae  var. mazae  Ziesenhenne / section Gireoudia / Mexico / glabrous, triangular, acuminate stipules

Elliptic-ovate

Acuminate (narrowing gradually and then ending abruptly in a fine point) or not:

    • B. convalloriodora C. de Candolle / section Ruizopavonia / Mexico – Central America / acuminate stipules

Cuspidate

Tapering to a sharp, stiff point that forms a sharp angle with the edge.

Long-attenuate

Whose width decreases gradually.

Navicular

Boat- or shuttle-shaped.

The two stipules are sometimes different, the outer one enveloping the second (inner) one and the bud that will become the leaf.

    • B. mannii  W J Hooker / section Tetraphila / from Guinea to Gabon / the outer stipule envelops the bud of the future leaf and the inner stipule

They sometimes have a midrib that is prominent, and a fold along this midrib.

    • B. venosa Skan / section Begonia / Brazil / stipules with a clearly marked midrib

Appearance

The outside of the stipules can be glabrous or hairy over their whole surface.

    • B. listada LB Smith & Wasshausen / section Pritzelia / Brazil – Paraguay – Argentina / stipules hairy all over

The margin

Denticulate or Serrate

With small teeth like those of a saw.

Fimbriate

Edge densely and finely cut.

Ciliate

Edge with hairs (often extending the teeth of the margin).

B. Philippines sp. / stipule margin finely toothed and ciliate