The most commons trees are elm, alder, sycamore, poplar, willow and hornbeam. River valleys contain willow, poplar and caragana shrubs. A common staple was fish eggs with willow or birch bark. The nest is built in cattails, rushes, grasses, sedge, or in alder or willow bushes. Yupik medicine used dried beaver testicles like willow bark to relieve pain. Other species include willow and alder (along stream courses) and bay laurel. Willow trees and reeds absorb salt and other contaminants, effectively desalinating the water. Many species of willow and other shrubs grow in virtually any terrain. Sand was used as a fill material between reed and willow layers. The term translates as "the flower and willow world". Warren bears a considerable grudge against both Willow and Buffy. Buffy convinces Giles of her identity with the help of Willow and Tara. Buffy now identified with the social outcasts, such as Willow and Xander. He appeared as kidnapper Reggie in the "" episode "Weeping Willow". The frame was covered first with smaller poles, tied with willow withes.