o 



218 A T^TT-BOOK OF BOTANY 



it is packed nutritive tissue (often called endosperm), which 

 is the female gametophyte; and outside of that there is 

 found the bony seed-coat- (testa). In 

 thfs condition of suspended animation 

 the* embryo may continue for a long 

 time, certainly until the next season, 

 FIG. 206.-section of per haps for many seasons. ' When the 



a pine seed, showing * * 



embryo (young spo- seed comes into favorable conditions 

 and "awakens," the embryo escapes 



male gametophyte), an( j[ grows into the pine-tree. This 



which is invested by . 



the hard testa. awakening of the seed is usually called 



its "germination," but it must not be 

 confused with the germination of spores and oospores. 

 The "germination" of the seed is merely the resumption 

 of growth by the embryo and its escape from the seed. 

 In seed-plants, therefore, there are two distinct periods in 

 the growth of the sporophyte, the period within the seed 

 (when it is called an embryo), and the period outside of 

 the seed; and these two periods may be separated from 

 one another by a long period of time. For an account of 

 seed germination see Chapter V. 



128. Timber from Conifers. The conifers are the most 

 important source of timber in the United States, yielding 

 at least three-fourths of our supply. They are usually 

 called "soft woods" in distinction from the so-called 

 "hard woods," such as oak; but there are soft and hard 

 woods in both groups. The United States is notable for its 

 variety of pines, broadly grouped into the soft white pine 

 and the hard yellow pines. Our principal supplies come 

 from the white pine forests about the Great Lakes and the 

 yellow pine forests of the Southern States; but the forests 

 of the former region have been cut over so ruthlessly for so 

 long a time that the supply of white pine is diminishing. 

 A few years ago the white pine furnished nearly one-third 

 of all the timber produced by the United States. It is very 



