不同寻常的植物——仙人掌

Unusual Plants

When you think of the deserts(沙漠),you probably think of cactuses,their strange shapes and sharp spines(尖刺).But why do they look like this?Also,how do they manage to survive(生存)in a hot,dry desert?Their sharp spines are part of the secret to their success.Let's find out why!