THE SPECIES. 21 



The cone fruit is matured in one or two years. Some species then 

 spread apart the scales of the cone upon drying and allow the seeds 

 to fall out; they are carried away by tihe wind. Seeds thus dis- 

 tributed are usually provided with an ample and thin membranous 

 wing and a kernel of oily material that is somewhat lighter in weight 

 than starch, a common reserve material in seeds distributed by other 

 means. Seeds of this group of plants have usually a hard outer shell 

 inclosing a mass of rich oily food material, in the center of which 

 is embedded the germ or embryo. The latter is the young tree, con- 

 sisting of a cylindrical stem terminated at one end by the initial root 

 structure, and at the other by seed leaves or cotyledons to the number 

 of two or more. The food material serves the young plant until it 

 becomes established in the soil; the seed leaves then spread apart 

 and remain throughout the first season as leaf-like structures. 



The seeds of most conifers under proper conditions germinate in 

 one to two weeks. With some exceptions they are of transient via- 

 bility. Conifers as a class have leaves of hard or leathery texture, 

 which lessens the amount of moisture they impart to the air ; conse- 

 quently they are often found in situations too dry for broad-leaved 

 trees. They are trees of hardy nature, are widely and abundantly 

 distributed over the earth, and are plants of ancient origin, whose 

 ancestors were a dominant type of vegetation in earlier periods of 

 the earth's history. 



The members of the pine family are classified mainly upon the 

 basis of the form and structure of the' leaves and cones, though other 

 features, such as the arrangement of the leaves, qualities of the wood, 

 and the characters of the bark, are likewise important. Beyond these 

 characters each species has its own peculiar limitations as to light, 

 temperature, moisture, and other factors which influence, or deter- 

 mine, its local and general distribution. 



THE PINES. 



The pines are easily recognized by the form and arrangement of 

 their leaves, which are usually from 2 to 6 inches in length, needle- 

 like and clustered in twos, threes, or fives. They are borne thus on 

 short lateral branches, accompanied by a scale or bract inserted on 

 the main branch just below the position of the short lateral. Some 

 species shed these bracts early ; others retain them for several years. 

 Species also differ in the length of time during which they retain 

 their foliage leaves. All are bound to fall at some time, but new 

 leaves come out every spring while the leaves of other years are still 

 upon the branch, so that the tree is never without leaves. On some 

 pines the leaves remain for 2 years, in others for 3, 4, 5, or even 12 

 years. When they fall they take with them the small twig on which 



