Basilicum polystachyon (L.) Moench

Global description

Basilicum polystachyon is an erect, branched, almost glabrous, annual herbaceous plant of medium height (30 cm to 1 m) with a quadrangular stem. The simple and opposite leaves are oval to oval-rhombic, irregularly toothed. The small pale-purple flowers are arranged in axillary and terminal spikes. The fruit is a compressed achene with a smooth surface of brown color.

Cotyledons

The cotyledons are borne by a petiole (1 to 1.5 mm long) scattered with erect hairs. The lamina is broadly oval (sub-trapezoidal), with an obtuse base and emarginate apex, with an entire margin. It measures 1.5 to 2.1 mm long and 2.6 to 3.5 mm wide and has some scattered short hairs.

First leaves

The first 2 leaves are short stalked (petiole 0.5 mm long with sparse pubescence of stiff bristles). The blade is oval, obtuse to cordate base, rounded apex, toothed margin to crenate. It is 3.5 to 6 mm long by 2.5 to 4.2 mm wide and has scattered stiff hairs. The venation is pinnate. The margin is densely and shortly ciliated.

General habit

An erect, very branched, almost hairless, annual herb that is 30 cm to 1 m tall.

Underground system

The root is a taproot.

Stem

The stem is quadrangular in section and glabrous.

Leaf

The leaves are simple, opposite and decussed. The petiole is elongated. It is 8 to 50 mm long. The limb is fine. The two faces are almost glabrous: some erect hairs are scattered on the veins and on the upper face. The underside is densely punctuated with glands. The lamina is oval, oval-oblong to oval-lozenge-shaped, wedge-shaped, with an end gradually terminating in a point. The margin is irregularly toothed. It measures 2 to 7 cm in length and 1.8 to 3.5 cm in width.

Inflorescence

The flowers are grouped by whorls of 6 to 10 flowers, assembled in dense racemes, spiciform, 2 to 10 cm long, terminal and / or axillary. The main peduncle has few but very visible hairs. The bracts are obovate, with an obtuse-truncated or mucronate end. They measure 0.7 to 2 mm long and are persistent.

Flower

The flower is short pedicelled (0.3 to 0.7 mm). It is approximately 2.5 mm long. The calyx is an elongate tube (1.8 to 2 mm long) extended by 5 teeth (a broad, blunt tooth suddenly terminated in a point, the other 4 triangular). It is bristly with stiff hairs clearly visible on the outside, with a very fine and sparse pubescence inside. The corolla consists of a tube extended by 2 lips. It is 2 to 2.5 mm long. It is of a mauve-pale color almost white. The upper lip consists of 3 obtuse oval lobes, the lower lip of a single flat or barely concave lobe. The 4 stamens leave the tube of the corolla. They are grouped in 2 pairs of unequal lengths. The pistil exceeds the tube of the corolla. It consists of 4 ovaries grouped at the base of an elongated style and ended with a short bifurcated stigma.

Fruit

The fruits ripen in the evergreen calyx the width of which increases after flowering. The fruit is an oblong and globular compressed achene. Its surface is smooth, of a matt brown color. It is 0.5 mm long.

https://www.gbif.org/species/3882375