STEMS I 2 I 



under the soil as well as above it. These under- 

 ground stems resemble roots but can be distin- 

 guished from them by the rings or joints where 

 will be found buds and small scale-like leaves (Fig. 

 69). Quitch-grass or wiregrass, Burmuda grass, 

 white potato and artichoke are examples of under- 

 ground stems. 



Now study the habit of growth of these stems. 

 Notice that: 



Some plants grow erect with strong, stiff steins, 

 for example, corn, sunflower, maple, pine, elm and 

 other trees. Many of these erect stems have 

 branches reaching out into the air in all directions. 

 Stand under a tree close to the stem or trunk and 

 look up into the tree and notice that the leaves are 

 near the outer ends of the branches while in the 

 centre of the tree the branches are nearly bare. Why 

 is this? If you remember the work of leaves and 

 the conditions necessary for their work you will 

 be able to answer this question. Leaves need light 

 and air for their work, and these erect, branching 

 stems hold the leaves up and spread them out in 

 the light and air. 



Notice that where several trees grow close to- 

 gether, they are one-sided, and that the longest and 

 largest branches are on the outside of the group 

 and that they have more leaves than the inner 

 branches. Why ? Why do the trees in thick woods 

 have most of the living branches and bear most of 

 their leaves away up in the top of the tree? 



Some stems instead of standing up erect climb 



