48 HOUGH'S AMERICAN WOODS. 



PHYSICAL PROPERTIES. Wood soft, light, close-grained, with many thin 

 medullary rays, and of a warm, reddish brown color with lighter sap-wood. 

 Specific Gravity, 0.4930; Percentage of Asli, 0.48; Relative Approximate 

 Fuel Value, 0.4906 ; Weight of a Cubic Foot in Pounds, 30.72. 



USES. -- The wood is sometimes used for light fuel and charcoal, but the 

 great value of the tree lies in the part which it plays in the economy of 

 nature, in fixing the banks of streams from erosion by its long roots and 

 steins. It is usually the first tree in many localities to take possession of 

 sand-bars, as soon as they appear sufficiently above water, and in course of 

 time the Sycamores and other sturdy riparian trees are able to gain footing 

 under the protection afforded by the little willows. 



GYMNOSPERMJE. 



Flowering, exogenous plants with leaves chiefly parallel-veined and cotyledons frequently 

 more than two. Floivers diclinous and very incomplete; pistil represented by an open 

 scale or leaf, or altogether wanting, with ovules naked, fertilized by direct contact with 

 the pollen, and seeds at maturity naked without a true pericarp. 



ORDER CONIFERS : PINE FAMILY. 



Leaves mostly awl-shaped or needle-shaped, evergreen, entire and parallel-veined. 

 Flowers monoecious, or rarely dioecious in catkins or cones, destitute of both calyx and 

 corolla; stamens one or several (usually united) ; ovary, style and stigma wanting; ovules 

 one or several at the base of a scale, which serves as a carpel, or on an open disk. Fruit 

 a cone, woody and with distinct scales, or somewhat berry-like, and with fleshy coherent 

 scales, seeds orthotropous, embryo in the axis of the albumen. 



Trees or shrubs with a resinous juice. 



GENUS PINUS, TOURNEFORT. 



Leaves evergreen, needle-shaped, from slender buds, in clusters of 2-5 together, each 

 cluster invested at its base with a sheath of thin, membranous scales. Flowers appearing 

 in spring, monoecious. Sterile flowers in catkins, clustered at the base of the shoots of 

 the season ; stamens numerous with very short filaments and a scale-like connective ; 

 anther cells, 2, opening lengthwise ; pollen grains triple. Fertile flowers in conical or 

 cylindrical spikes cones consisting of imbricated, carpellary scales, each in the axil" 

 of a persistent bract and bearing at its base within a pair of inverted ovules. Fruit 

 maturing in the autumn of the second year, a cone formed of the imbricated carpellary 

 scales, which are woody, often thickened or awned at the apex, persistent, when ripe dry 

 and spreading each to liberate two nut-like and usually winged seeds; cotyledons 3-12, 

 linear. 



(Pinus is a Latin word from Celtic pin or pen, a crag.} 



