62 



BEGINKEKS' BOTA.VY 



Fig. 73. — The 

 Scattered 

 Bundles or 

 Strands, in 

 monocotyledons 

 at a, and the bun- 

 dles in a circle in 

 dicotyledons at b. 



Fig. 74. —Dicotyledonous Stem of One Year at Left 



WITH Five Bundles, and a two-year stem at right, 

 o, the pith; c, the wood part; ^, the bast part; rf, one year's growth, 



rittg. As the dicotyledonous seed germi- 

 nates, five bundles are usually formed in 

 its hypocotyl (Fig. 74); soon five more are 

 interposed 



b etween 

 them, and 

 the multi- 

 plication continues, in 

 tough plants, until the 

 bundles touch (Fig. 74, 

 right). The inner parts 

 thus form a ring of wood 

 and the outer parts form 

 the inner bark or bast. A 

 new ring of wood or bast 

 is formed on stems of di- 

 cotyledons each year and 

 the age of a cut stem is 

 easily determined. 



When cross-sections of 

 monocotyledonous and di- 

 cotyledonous bundles are 

 examined under the mi- 

 croscope, it is readily seen 



Fig. 75. — FiBRO-vAscuLAR Bundle of 

 Indian Corn, much magnified. 



Af annular vessel ; A', annular or spiral vessel ; 

 TT' , thick-wallcd vessels; W, tracheids or 

 woody tissue ; F, sheath of fibrous tissue sur- 

 rounding the bundle ; FT, fundamental tissue 

 or pith ; S, sieve tissue ; P, sieve plate ; C, 

 companion cell ; /, intercellular space, formed 

 by tearing down of adjacent cells ; IV' , wood 

 parenchyma. 



