CHAPTEE V. 



Steins. 



57. What the Stem is. — The work .of nourishing the 

 plant is done mainly by the roots and the leaves. The stem 

 is that part or organ of the plant which serves to bring roots 

 and leaves into communication with each other. In most 

 flowering plants the stem also serves the important purpose 

 of lifting the leaves up into the sunlight, where alone they 

 best can do their especial work. 



The student has already, in Chapter II, learned some- 

 thing of the development of the stem and the seedling ; 

 he has now to study the external appearance and internal 

 structure of the mature stem. Much in regard to these can 

 conveniently be learned from the examination of twigs and 

 branches of our common forest trees in their winter condition. 



58. The Horse-Chestnut Twig.''- — Procure a twig of horse-chestnut 

 eighteen inches or more in length. Make a careful sketch of it, trying to 

 hring out the following points : 



(1) The general character of the hark. 



(2) The large leaf-scars (marking the places where the bases of leaf- 

 stalks were attached) and the number and position of the dots on these 

 scars. 



(3) The ring of narrow scars around the stem in one or more places,^ 

 and the different appearance of the bark above and below such a ring. 



See Fig. 23, 6 sc. 



(4) The buds at the upper margin of each leaf-scar and the strong 

 terminal bud at the end of the twig. 



1 Where the buckeye is more readily obtained it will do very well. Hickory 

 twigs answer the same purpose, and the latter is a more typical form, having alter- 

 nate bnds. The magnolia or the tulip tree will do. The student should (sooner or 

 later) examine at least one opposite and one alternate-leaved twig. 



2 A very vigorous shoot may not show any such ring. 



