Spines are modified leaves. They can be found on the nodes of cacti (as can be seen in both types of cacti in the picture). Spines serve to prevent water loss and protect the plant against consumers. In the small round species of cactus, the spines are long and thin. This is beneficial because they absorb and condense moisture which drips and is absorbed by the roots. Spines also provide shade to the cactus and trap air close to the surface, creating a moisture layer that prevents evaporation and transpiration.