THE STEM. 21 



THE STEM. 



17. The most striking differences in stems of various 

 plants is in regard to their size and texture. A stem 

 whose tissue is soft (mostly green) and not -woody is said to 

 be herbaceous. An herb which completes its growth 

 and dies the same season is called an annual; a bienmal 

 herb, such as the Turnip, Carrot, etc., requires two years to 

 complete its growth and produce seed ; an herb is perennial 

 when the root continues to live for several years, although 

 the stem every year dies down to the ground, a very small 

 portion only remaining, from the buds of which the shoots 

 arise the following year. If the stem is woody, though not 

 growing to a great height, it is said to be fruticose (Lab 

 frutex, shrub), or shrubby ; when 

 approaching a tree in size it is arbor- 

 escent (Lat. arbor, tree), and when 

 forming a proper tree-trunk it is ar- 

 boreous. 



18. The stem of every plant is ver- 

 tical in its early stages of development ; this direction is 

 often maintained, when the stem is said to be erect. If 

 it is prostrate or trailing it is said to be procumbent. 

 A decumbent stem is one that reclines on the ground 

 after having arisen at the base somewhat above it. A stem, 

 climbing by tendrils or rootlets, is said to be scandent ; 

 when twining around other objects it is voluble. Stems 

 which grow underground are called subterranean stems. 



ig. The majority of stems and branches are more or less 

 round (Fig. 9), but many of our common plants, for exam- 

 ple, the whole family Labiatce (" lip-shaped flowers''), have 



Fig. 9. A round stem. Fig. 10. A square stem. Fig. 11. A flattened stem. 

 Fig. 12. A winged stem. 



