Thorns, spines and prickles

Botanists use three different words for sharp things on plants. They are thorns, spines, and prickles. Thorns are the ends of branches that are hard and sharp. Spines are hard structures with sharp ends. There are many different kinds of spines. Some are on leaves, and some grow instead of leaves. Prickles are on the outside of stems.

Spines, prickles, and thorns protect plants from plant-eating animals (defence against herbivory). Some plants and animals, such as the acacia tree and giraffe have evolved in response to each other. The plants grow very long spines and the animals develop very long tongues to reach past the spines and feed on the leaves.

Gallery

Prickles on rose stems
A thorn is a branch with a sharp tip
Spines of this Ocotillo were leaves that have died
Spines on this Acacia grow below the leaves (the stem is sideways in the picture)

Thorns, Spines And Prickles Media

Prickles on a blackberry branch
Thorns are modified stems and arise from buds
Cactus areoles; shoot (yellow), spines (green) and glochids (also spines, green and little)
(A) Thorn or spine(B) Prickle
A spinose tooth in a leaf margin
Proceso apical de forma bidimensional espinoso o pungente, según Simpson (2005), Plant Systematics.
"Root spines" on the trunk of a Cryosophila species.
Smooth, featureless Citrus thorn.
Carissa bispinosa showing characteristic branched thorns.

References

Esau, K. 1965. Plant Anatomy, 2nd Edition. John Wiley & Sons. 767 pp.
Llamas, K. A. 2003. Tropical Flowering Plants. Timber Press, Portland. 423 pp.