140 TAN. NUT-GALLS. CORK. 



form long, slender catkins at the upper part of the young 

 branches ; and the female flowers are sessile, and grouped in the 

 axils of the upper leaves. This tree grows slowly, but lives for 

 a long time ; it rarely begins to bear glands (acorns) at an early 

 age, but does not cease to grow till the end of three or four cen- 

 turies. Its wood is very valuable on account of its hardness and 

 durability, and is used for frame-work in building. Its bark, 

 which is very astringent, is also very useful, because it serves to 

 make tan, a substance by means of which skins are tanned, and 

 form leather. 



122. Nut-galls, which are employed for making ink, and for 

 dyeing black, are excrescences produced by the sting or puncture 

 of a little insect on the branches of a species of oak in Asia 

 Minor. 



123. The holm-oak or evergreen-oak which abounds in the 

 South of Europe, has dentate leaves, which remain throughout 

 the winter. The same is true of another species of this genus, 

 known as the cork tree, because it furnishes cork. This sub- 

 stance, which is spongy and elastic, is the herbaceous layer of 

 the bark, which is removed from the tree every eight or ten 

 years ; there are a great many of these trees in Spain, and also 

 in the South of France. The outer bark is the cork, but there 

 is an interior bark which is left on to protect the tree, so that 

 stripping off the outer bark is so far from injuring the trees, that 

 it is necessary to their continuation. Trees that are never bark- 

 ed are said to die at the end of fifty or sixty years. The bark 

 is removed for the first time when the tree is about fifteen years 

 old. It is taken off in sheets, and after being detached, it is flat- 

 tened by presenting the convex side to heat, or by pressure. In 

 either case it is charred (slightly burned) on both surfaces to 

 close the transverse pores previously to being sold. The car- 

 bonized surface produced by this charring may be seen in bungs 

 (for casks), but not in corks, which being cut in the lengthway 

 of the bark, the charring is taken off in the rounding. 



124. The live-oak Quercus virens grows to the height of 

 forty or fifty feet, spreading its branches, when in open places, 

 extremely wide ; it yields the finest and most durable ship-timber 

 of any species known ; for which reason it is considered one of 

 the most valuable trees in the United States. It is chiefly found 

 in Florida, and the Southern States. 



122. What are nut-gails ? What are they used for ? 



123. What tree furnishes cork ? What is the reason that we see sheets 

 of cork slightly charred ? 



124. Where does live-oak grow ? 



