Citation: Lindley, Edwards' Bot. Reg. 12:t. 964 (1826).

Derivation: Greek isos, equal; tomos, a cutting; referring to the equally cut corolla lobes.

Synonymy: Lobelia sect. Isotoma R. Br., Prod. Fl. Nov. Holl. 565 (1810).

Common name: Isotomes.

Description:
Annual or perennial herbs with a distinct tap root but sometimes also with adventitious roots along the branches; leaves alternate, often petiolate at the base becoming sessile on the branches, exstipulate, toothed or lobed, rarely entire.

Inflorescence racemose to solitary flowers, with leaf-like bracts, the pedicel (or peduncle) often several times the length of the flower; calyx with a very short tube, persistent; corolla salverform with entire tube, the lobes subequal but often with distinct markings on the lower 3 lobes; stamens fused into a column around the style; anthers with the 3 upper slightly longer and at the apex more or less curved down onto the 2 shorter lower anthers with a terminal tuft of hairs as well as 2 bristles next to one another; ovary inferior to semi-inferior, 2-celled, the slender style topped by a slightly swollen more or less hairy and scarcely 2-lobed stigma eventually protruding from the anther-column.

Fruit a capsule splitting at the apex at first loculicidally then septicidally.

Distribution:  About 10 species endemic in Australia and 1 species in Central and South America.

Biology: No text

Taxonomic notes: F. E. Wimmer (1953) Pflanzenreich 276b (107):398 reduced Isotoma to sectional rank of the otherwise African and North American genus Laurentia (Mitcheli)Adans. However, the original circumscription is here maintained following R. Melville (1960) Kew Bull. 14:277-79 who provided some evidence for distinguishing the two genera on the basis of their pollination biology.

Key to Species:

1. Leaves sharply lobed and toothed; corolla tube 14-20 mm long	I. petraea 2.
1. Leaves entire to toothed (usually with blunt apices); corolla tube 3.5-8 mm long
2. Prostrate herb with leaves widely spaced; flower buds spreading; fruits smooth	I. fluviatilis 1.
2. Annual herb with leaves densely clustered at the base; flower bud nodding; fruit ridged	I. scapigera 3.

Author: Not yet available