Thorns

(Crataegus) This is a large group of hardy, deciduous trees and a few shrubs that are commonly known as Hawthorns or Thorns; other common names will be mentioned by its tree. Most of the Hawthorns are natives of North America; others are natives of Europe, Asia Minor, China, Japan, the Old World and the Himalayas. Hawthorns are beautiful, flowering...
Found on http://www.encyclo.co.uk/local/10004

Thorns

Stems modified to protect the plant.
Found on http://www.superglossary.com/Glossary/Science/Biology/
No exact match found