e leaves are borne alternately on the stem. In most species, they are 5 to 15 centimetres (2.0 to 5.9 in) long, pinnate, with (3–) 5–9 (−13) leaflets and basal stipules; the leaflets usually have a serrated margin, and often a few small prickles on the underside of the stem. Most roses are deciduous but a few (particularly from Southeast Asia) are evergreen or nearly so. Thorns The sharp growths along a rose stem, though commonly called "thorns", are technically prickles, outgrowths of the epidermis (the outer layer of tissue of the stem), unlike true thorns, which are modified stems. Rose prickles are typically sickle-shaped hooks, which aid the rose in hanging onto other vegetation when growing over it. Some species such as Rosa rugosa and R. pimpinellifolia have densely packed straight prickles, probably an adaptation to reduce browsing by animals, but also possibly an adaptation to trap wind-blown sand and so reduce erosion and protect their roots (both of these species grow naturally on coastal sand dunes). Despite the presence of prickles, roses are frequently browsed by deer. A few species of roses have only vestigial prickles that have no points.[citation needed] Plant geneticist Zachary Lippman of Cold Spring Harbor Laboratory found that prickles are controlled by the LOG gene. Blocking the LOG gene in roses reduced the thorns (large prickles) into tin