Leaf Terminology (Part 1)

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Botany 115 Terminology

Leaf Terminology Part 1

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Inflorescence Terminology Part 1
Inflorescence Terminology Part 2

1. Simple Leaf: One Blade

2. Compound Leaf: Blade Divided Into Leaflets

A. Palmately Compound (Digitate): No Rachis

B. Pinnately Compound (Pinnate): With A Rachis

C. Pinnately and Palmately Trifoliate

Left: basket bush (Rhus trilobata), also referred to by the politically incorrect name of squaw bush; center: poison oak (Toxicodendron diversilobum); right: Baja California poison ivy (T. radicans ssp. divaricatum).

D. Twice Pinnately Compound (Bipinnate)

Although some references use the term "pinna" for a compound leaflet of a
bipinnate leaf, this term should only be used for the leaflet of a pinnate leaf.

E. Pinnatid: Pinnately Dissected Nearly To The Midrib

See Native Hawaiian Ferns

3. Leaf Arrangement (Phyllotaxy)

Three different leaf arrangements: Alternate (one leaf per node), opposite (two leaves per node) and whorled (three or more leaves per node). A node is the place where one or more leaves are attached along the stem. The area between the nodes is called the internode.

4. Leaf Venation

Leaf venation in two species of Ceanothus. C. leucodermous has glaucous leaves with three main veins from the base. This is a thorny (spiny) chaparral shrub with rigid, sharp-pointed branchlets. It is common on Palomar Mountain in San Diego County. C. palmeri has pale green leaves with one main vein from the base. This shrub is also common on Palomar Mountain, particularly in Doane Valley.

See Vegetative Terminology (Parts I, II, III)
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