WILLOW 155 



SALICACE-ffi, OR WILLOW FAMILY 



This family consists of two genera, viz.: Salix and Populus, and 

 of which there are 200 or more species. They are mostly native of 

 the north temperate zone, some growing in the Arctic regions and 

 necessarily being of diminutive stature. The willows usually grow 

 in wet ground and are sometimes used, like the Australian eucalyptus, 

 in drying out damp ground especially where the conditions are unsan- 

 itary. The willows are extensively cultivated not only for orna- 

 mental purposes but for economic purposes. The twigs are used in 

 the making of baskets, and the wood furnishes a charcoal which is 

 employed in medicine and in making crayons and gunpowder. The 

 " pussy willow " (Salix discolor) is a small tree rather common in low 

 meadows and river banks and is marked by thick cylindrical aments, 

 the scales being copiously clothed with long glossy hairs. The Pop- 

 lars are sometimes planted because of their rapid growth as shade 

 trees. They are also grown to serve as windbreaks in the Western 

 States. The wood is largety used in making paper, card-board, etc. 

 The balsam-poplar or tacamahac (Populus balsamifera) and balm of 

 Gilead (P. candicans) are well-known trees of the United States and 

 distinguished by their large buds, which are copiously covered with 

 a fragrant resin. 



Some of the important anatomical characteristics of this family 

 are the following: In the stem there is a superficial development of 

 the periderm and isolated bundles of bast fibers : the medullary rays 

 are from 1 to 2 cells in width; the trachea usually possess simple 

 pores and the wood parenchyma, which is scantily developed, con- 

 tains thick, porous walls. In the leaves the inner walls of the epi- 

 dermal cells may be modified to mucilage; the stomata are accom- 

 panied by subsidiary cells arranged parallel to the pores, the hairs 

 are of the simple unicellular type, and the leaf-teeth may become 

 glandular, excreting an excess of balsam in certain species of Salix 

 and Populus. Calcium oxalate occurs in the form of rosette aggre- 

 gates and solitary crystals. In some cases the pith may contain a 

 deposition of carbonate of calcium. 



SALIX. Cortex Salicis, Willow Bark. The bark of Salix alba 

 (Fam. Salicaceae), a noble tree indigenous to Europe, .and nat- 

 uralized in the northern United States and Canada. In the spring 

 of the year the bark is stripped from the two or three year old branches 

 and quickly dried. The commercial article frequently consists in a 

 large part of the bark of more mature branches or the trunk of young 

 trees and is frequently deprived of the periderm. 



