CONIFERS. 



191 



produced in a whorl ; the distance between the whorls being 

 the growth of each year, in that respect analogous to the in- 

 crease in the stem of Cycads consequent on the annual de- 

 velopment of a whorl of leaves, as explained in the Cycads ; 

 the leaves of which being long permanent may be viewed as 

 partaking of the nature of branches. The leaves of the genus 

 Pinus, Araucaria, and others, agree with those of Gycas in 

 having a midrib only ; while the broad leaves of Dammara 

 have longitudinal veins without a midrib, and thus coinciding 

 with Zamia Skinneri and other American species. The 

 structure of the wood of Coniferge differs from that of other 

 trees (Magnolia excepted) in the tissue containing numerous 

 circular clear dots arranged in lines, which may be seen by 

 placing a thin shaving from any kind of fir- wood on glass, 

 moistened with water, and viewed under the microscope. 



With the exception of food-producing families, Coniferse 

 may be viewed as the next in importance to man in many 

 countries. They are not only valued for their timber, but 

 also for their products of tar, pitch, and turpentine. In 

 this country the timber known as pine, fir, and spruce is the 

 principal wood employed in house and shipbuilding and 

 erections of all kinds ; also for making implements, and 

 many articles of domestic economy, even lucifer-matches. 

 Under certain conditions coniferous wood appears to be in- 

 destructible ; in the north of Scotland trees are found im- 

 bedded in peat bogs ; their resinous nature and the antiseptic 

 property of the peat preserves them from decay. They are 

 split into laths, and used as candles, the resin they contain 

 causing them to burn with a steady flame. The hard resinous 

 knots common to fir timber are formed by the bases of the 

 dead branches becoming imbedded in the body of the tree. 



The numerous piles lately discovered in the Swiss lakes 

 are found to be coniferous wood, and being pre-historic must 

 be viewed as the oldest remains known of the work of man on 

 wood (page 120). 



