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TEXTBOOK OF BOTANY 



of the radicle, just below the point of attachment of the seed 

 leaves, forms the base of the stem. 



As the radicle and the seed leaves grow, the latter, which 

 have already begun to form chlorophyl, are pushed above 

 the surface of the soil. The upper end of the radicle becomes 

 upright, the seed leaves spread out, and the plant, now pro- 

 vided with a root and leaves, is ready to make its own way in 

 the world. The old seed coats, with what is left of the en- 

 dosperm, are usually canied upward on the ends of the seed 

 leaves, and as the leaves grow and spread out, the seed coats 

 are thrown off. As the primary root grows into a long tap 

 root, branch roots are formed. The plumule forms all of the 

 stem excepting its very base. For a time, foliage leaves are 

 borne directly upon the stem and its long branches ; these 

 early leaves are comparatively short and flatter than the later 

 leaves. In the course of a few months, spur branches begin 

 to appear, which bear foliage leaves of the ordinary kind ; 

 and from this time on, all the new foliage leaves are borne on 

 spur branches. 



156. Life Cycle of the Pine. — The course of events in the 

 life of the pine can be understood only by comparing it with 

 such plants as the moss and the fern. This comparison was 

 first clearly made by Hofmeister (182 4- 1877), who showed 

 in this way the real nature of the different parts of the pine 

 cones as well as that of the parts of an angiosperm flower. 

 The central fact in the life of the moss, the fern, or the pine 

 is the occurrence of two distinct generations — an asexual 

 generation that reproduces by means of spores, and a sexual 

 generation that reproduces by means of gametes. While 

 the fern and the pine are alike in this central fact of having 

 two generations, the pine is different from the fern in the 

 following respects : 



a. In the formation of two kinds of spores, of which one 

 grows into a male plant and the other into a female 

 plant. However, this is not peculiar to seed plants (of 



