The thorn is a hard, straight and pointed structure. In Citrus and Bougainvillea the axillary bud is modified into a thorn. Cucumber and pumpkins have long slender and coiled stem tendrils which develop from axillary buds. Stem is flattened and fleshy in Opuntia and modified to perform photosynthesis. Rhizophora shows vertically upward growing roots which is known as pneumatophore help to get oxygen for respiration. Subaerially growing stems in grasses and strawberry help in vegetative propagation.