250 BOTANY AND PHARMACOGNOSY. 



II. ORDER SALICALES. 



This order comprises but a single fanlily, namely, the Sali- 

 CACE^E or Willow Family, to which belong the willows and pop- 

 lars. The plants are dioecious shrubs and trees ; the flowers being 

 in aiiiciifs or catkins and without petals or sepals. The fruit is a 

 capsule containing many seeds which are small and with long silky 

 hairs at the base. 



The barks of a number of the members of this group contain 

 glucosides, as salicin which is found in Salix alba the white willow 

 of Europe and the United States, and the brittle willow Salix fra- 

 gilis; and populin which is found in the white or silver-leaf pop- 

 lar {Populus alba) of Europe, Asia and the United States and 

 Popnhis pyramidalis of Italy. These principles are also found in 

 other species of willow and poplar. A number of the barks con- 

 tain a yellow coloring principle allied to quercitrin, as Salix daph- 

 noidcs of Europe and Salix alba. Tannin is a common constit- 

 uent in both the willows and poplars. The buds of many of the 

 poplars contain in addition a volatile oil which is in the nature of 

 a di-terpene, as those of Populus pyramidalis. Po pubis balsam- 

 ifera, the tacamahac or balsam poplar of the United States and 

 Canada, furnishes the balm of Gilead buds which are coated 

 with an oleo-resin that gives them their aromatic properties. Pop- 

 ulus nigra yields a volatile oil of which the important constituent 

 is humulene. 



The charcoal used medicinally is prepared by burning the 

 wood of the young shoots of the white and black willow, poplar, 

 beech or linden without access of air. 



III. ORDER MYRICALES. 



This group somewhat resembles the Salicales in that the 

 flowers are in aments. The flowers are either pistillate or stam- 

 inatc and mostly dioecious in our native species. The most im- 

 portant fimilv is the AIyricace.e or Bayberry Family. The 

 genus Mvrica is especially characterized by the fact that the outer 

 layer of the drupe is waxy. This is particularly true of the fol- 

 lowing species : Myrica ccrifcra the wax myrtle of the sandy 



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