No thorns are modified branches or stems.
Spines are modified leaves.
http://books.Google.com/books?id=8tz2aB1-jb4C&pg=PA576&lpg=PA576&dq=thorns+modified+branches&source=bl&ots=PEwba46CoC&sig=GfdegyPWKFEmtskyuRonTh3yGG4&hl=en&sa=X&ei=80epUMHaKtO-0QHJqYDoCQ&ved=0CHwQ6AEwDQ#v=onepage&q=thorns%20modified%20branches&f=false
Yes, Victoria Cruziana have thorns on the underside of their leaves and on their stems.
aloes normally have short, hard (sometimes black) spines on the leaves and sometimes the stems - although they cannot really be likened to black thorns
The desert cactus
the stem
Aloe vera actually has spines, not true thorns. They are to protect the plant from damage from animals that may want to eat them
defence. the cacti leaves are the thorns...
specialized leaves
Yes, Victoria Cruziana have thorns on the underside of their leaves and on their stems.
Yes
a desert plant with thorns but withouth leaves
Most varieties of hibiscus do not have thorns. However, gardeners have reported finding thorns on certain kinds of hibiscus bushes.
aloes normally have short, hard (sometimes black) spines on the leaves and sometimes the stems - although they cannot really be likened to black thorns
The desert cactus
Shrubs with pinnate leaves and thorns include various species within the genus Acacia, commonly known as acacias. These shrubs are characterized by their compound leaves, which are often divided into smaller leaflets, and they typically have sharp thorns for defense. Another example is the Gleditsia, or honey locust, which features pinnate leaves and possesses thorns along its branches. Both types of shrubs are often found in arid and semi-arid environments.
Wide, flat leaves, the thorns on the bottom of the leaves, the rims around the leaves and the short lifespan of the flower.
the stem
Aloe vera actually has spines, not true thorns. They are to protect the plant from damage from animals that may want to eat them