Imbricate:- Overlapping like tiles.
Imparipinnate:- Unevenly or odd pinnate i.e. with a single terminal leaflet, composed of multiple leaflets unevenly placed along the midrib
Impress - Impressed:- To be imprinted or marked by pressure, Indented.
Incised:- Cut rather deeply, this term is intermediate between toothed and lobed
Incise-dentate:- Deeply toothed
Incise-serrate:- With a deep saw-toothed margin.  margins deeply saw-toothed
Incrassate:- Thick, stout
Indumentum:- The covering of hairs or scales.
Indurate, Indurated:- Hard. Hardened.
Indehiscent:- Fruits that do not split open to release their seeds. not splitting open to release their seeds
Inferior:- Refers to flowers in which the ovary appears to lie below the other flower-parts (i.e. with sepals, petals and stamens at­tached to the top of the ovary).
The flowering branch or branches, flowers and bracts above the uppermost leaves on a stem. Inflorescences are very variable from one species to another.
Infundibuliform, Infundibular:- Funnel-shaped.
Intercalary:- (of growth) taking place between apex and base (but not at the apex or base).
Internode:- The portion of a stem between two nodes.
Introduced:- Not native. Thought on good evidence to have originated elsewhere.
Introrse:- (of anthers) Opening inwards, opening towards the centre of the flower.
Involucre:- Flower-bracts forming a cup or ruff surrounding the base of a flower cluster or head.
Invaginated:- Enclosed in a sheath.
Involute:- Leaf margins rolled inwards and upwards