What are the abnormal leaves of thorns, stems and leaves?

Stem thorn is a stem thorn, also known as a branch thorn, such as the single thorn of hawthorn, the branch thorn of lime and Gleditsia sinensis. Stem spines sometimes branch to produce leaves, which are often located in the axils of leaves, which is different from leaf spines.

The thorns on the stem of rose are formed by epidermis, which has nothing to do with vascular tissue and is obviously different from the thorns on the stem.

A leaf or a part of a leaf (such as stipules) becomes prickly, which is called a leaf thorn. There are buds in the axils of leaf thorns, which later develop into short branches with normal leaves on them. For example, the leaves on the long branches of Berberis become thorns, the stipules of Robinia pseudoacacia become thorns, and the thorns are in the stipules, which is easy to distinguish.