DURABILITY OF BIRCH BARK. 55 



where they stand for two years, and reach a height of 

 two or three feet, fit for finally planting out, they sell 

 at twenty-five shillings to thirty shillings per thousand, 

 which is thought a high price, when compared with 

 the firs which are sold by the nurserymen ; but not- 

 withstanding the disposition of the plant to grow wild, 

 and spring up spontaneously, it is generally the most 

 uncertain nursery crop of any hardy tree. 



The seeds are ripe in September usually, when 

 they are collected, and thinly exposed to dry in an 

 airy situation, to prevent fermentation, and when they 

 are quite dry, are put aside till March, when they are 

 sown. The beds are smoothly dug over, and the 

 seeds spread regularly on the surface, at the rate 

 of one bushel of seed to each bed of thirty lineal 

 yards. They want no covering, but require to be 

 pressed closely down into the ground with the feet. 



The bark of the birch is much in request for 

 tanning, and is especially preferred by fishermen for 

 preserving nets and cordage, being amongst the most 

 incorruptible of vegetable substances. 



The Elm. There are two leading species of the 

 elm. The U. campestris, or English elm, the tall 

 variety, which figures so prominently in most English 

 landscapes, and the U. montana, the mountain, or 

 Wych, elm, the genus Ulmus being the type of the 

 natural order Ulmacece. 



There are about twenty sorts of the U. campestris, 

 and botanists are unable to decide which are species 

 and which varieties. As it rarely produces seed in 

 England, it has been thought questionable whether it 

 is a native of this country; but if not truly indigenous, 

 it must have been introduced very early, and pro- 



