Entire shoot systems are often modified for such special functions as climbing, protection, adaptation to arid habitats, and water or food storage. The modifications generally involve structural and shape changes to the stem and the reduction of the leaves to small scales. Many of the modifications parallel those previously described for leaves. In the passion flower (Passiflora; Passifloraceae) and grape (Vitis vinifera; Vitaceae), axillary buds develop as tendrils with reduced leaves and suppressed axillary buds. In the grape these axillary tendrils are actually modified and reduced inflorescences. In the plant from which strychnine is obtained (Strychnos nux-vomica), the axillary buds develop into hooks for climbing.