The Legumes

Your book treats the legumes in the traditional way i.e. as one family the Fabaceae (= Leguminosae) composed of three subfamilies. Cronquist treated them as three families in the order Fabales.

For example:
Mimosaceae = Mimosoideae
Caesalpiniaceae = Caesalpinioideae
Fabaceae = Faboideae

All have a single, simple, superior carpel. Ovules vary from 2 to many and occur in alternating rows on either side of the suture.

The fruit is a "legume" by definition, but there is enormous variation in the morphology of fruits that are produced from the single carpel

The seeds lack endosperm - food stored in cotyledons

Most legumes have root nodules containing nitrogen-fixing bacteria
Enormous economic importance - second only to the grass family for food. Also, many ornamental plants.

Comparison of Mimosoideae, Caesalpinioideae, and Faboideae. See also Table 9.2 in your text.

Plant Sex: Flowers bisexual.

Flowers: Actinomorphic,5-merous. Stamens usually 10 or more. CA, CO, A usually connate but not adnate.

Inflorescence: Capitate clusters, spikes, racemes.

Fruits: Legume, dry, dehiscent along both sutures.

Habit: Mostly tropical and subtropical trees, shrubs, and herbs; few temperate members.

Leaves: Alternate, bipinnately compound, stipulate, with a PULVINUS (articulation at base of petiole).

Examples:
Albizia

A. julibrissin (mimosa tree). Flowering shoots.

Acacia

A. rigidula. Spiny branches. Flowering shoot. Dissected flowers.
A. farnesiana. Flowering and fruiting branches.
Examples of spine modifications: A. karroo, A. horrida, A. sphaerocephala, A. drepanolobium, A. cornigera with ants.
Examples of phylloclade-bearing species: from Malaysia, Costa Rica.

Inga

I. affinis. Flowering shoot. Flower. Flower L.S.

Mimosa

M. pudica (sensitive plant). Flowering shoot.

Pithecellobium

P. saman (Guanacaste tree). Habit of the tree.
P. guadalupense cat's claw). Flowering shoot. Fruiting shoot.
P. arboreum. Fruits with brightly colored legume walls contrasting with dark seeds.
P. species. Seeds with bright yellow arils.

Prosopis

P. juliflora (mesquite). Habit of tree. Flowering branches.
P. glandulosa (paper flower). Flowering branches. Inflorescence.

Calliandra

C. haematomma (powderpuff). Inflorescence.

SIUC / College of Science / Elements of Plant Systematics
URL: http://www.plantbiology.siu.edu/PLB304/Lecture17Fabal/Mimosoid.html
Last updated: 21-Mar-08 / dln