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TEXTBOOK OF BOTANY 



lengthened and new branches and leaves are formed during 



the growing season. 



At the coming of winter, growth stops and scale leaves 



covered with resin are formed that protect the bud. When 



growth begins again in the spring, the scale leaves drop off ; 

 but their bases remain, forming a ring 

 that looks like a thickening of the 

 stem. By means of this ring one can 

 see where the growth of one year 

 ended and that of the next year began. 

 From the thickened ring grow one or 

 more branches, which have developed 

 from buds in the axils of the fallen 

 scale leaves. If the terminal bud is 

 destroyed or killed, the growth of the 

 trunk ceases ; but commonly, in such 

 a case, one of the branches near the 

 top of the tree bends and grows up- 

 ward, so that the tree continues to 

 become taller. The stem of the fern 

 grows only in length ; but that of 

 the pine grows both in length and in 

 thickness. The trunk is slenderest 

 at the top and gradually thicker 

 toward the base, because the base 

 is the oldest part and has been 

 growing in thickness for the longest 

 time. 

 Inner Structiire of the Stem. — At the verj^ tip of 



Fig. 65. — A pine tree 

 that grew in a forest. 

 Photograph by L. S. 

 Cheney. 



140. 



the stem (Fig. 66) are many small cells, which, during the 

 growing season, are continually growing and dividing. In 

 this region, too, are some very small swellings ; these are the 

 beginnings of new leaves and branches. Below the tip the 

 cells are larger ; farther down tliey are still larger, and dif- 

 ferent groups of them are gradually taldng on the forms that 



