CHAPTER XXXIX. 



THE DIFFERENT TYPES OF STEMS. WINTER 

 SHOOTS AND BUDS. 



I. Erect Stems. 



715. Columnar type. The columnar type of stem may be 

 simple or branched. When branching occurs the branches are 

 usually small and in general subordinate to the main axis. The 

 sunflower (Helianthus annuus) is an example. The foliage part 

 is mainly simple. The main axis remains unbranched during 

 the larger part of the growth period. The principal flowerhead 

 terminates the stem. Short branches bearing small heads then 

 arise in the axils of a few of the upper leaves. In dry, poor soil, 

 or where other conditions are unfavorable, there may be only 

 the single terminal flowerhead, when the stem is unbranched. 

 The mullein i? another columnar stem. The foliage part is 

 rarely branched, though branches sometimes occur where the 

 main axis has become injured or broken. The flower stem is 

 terminal. The corn plant and the Easter lily are good illustra- 

 tions also of the columnar stem. 



Among trees the Lombardy poplar (Populus fastigiata) is an 

 excellent example of the columnar type. Though this is pro- 

 fusely branched, the branches are quite slender and small in 

 contrast with the main axis, unless by some injurj^or other cause 

 two large axes may be developed. As the technical nacol indi- 

 cates, the branching is fastigiate, i.e., the branches are crowded 

 close together and closely surround the central axis. The royal 

 Dalm and some of the tree ferns have columnar, simple stems, 



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