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Cacti are common in most desert systems. These hardy plants can go weeks without water.

Cactus thorns are modified stems that protect the plant from grazing animals. Spines of a cactus are modified leaves.


The corm is a relatively solid modified stem that has a few fleshy leaves. The node is the point where the leaf attaches to the stem. The presence of nodes and internodes makes the corm a modified stem. The papery tunic on the outside of a crocus corm is the dead petiole from last year's leaf. Corms also have a nonpersistent root system that lives only one season. In addition to normal fibrous roots, corms and some nontunicate bulbs have special roots (contractile roots). Because new corms develop on top of old, they are closer to the soil surface. Corms too close to the surface could suffer winter injury. Contractile roots are capable of becoming deeply anchored and contracting to pull the corm deeper into the soil. Thus corms can change their depth in the soil.

Examples: Crocus, Gladiolas