104 NATVBE-STUDY LESSONS. 



20. Make a cross-section and a longitudinal section of 

 the stems of the tulip and adder's tongue and as soon as 

 possible make similar sections of the stems of Indian- 

 corn and asparagus. 



21. Make drawings of these sections. 



22. Compare them with similar sections of the maple 

 and horse-chestnut twigs. 



23. Contrast the arrangement of the woody part in 

 the stem of the Indian-corn and in a branch of the maple 

 or horse-chestnut. 



24. (a) When trees ana shrubs are in full leaf, discover 



where there is much sap in the branches. 

 {b) Infer where growth is taking place. 



Stems like the maple and horse-chestimt aie said to be exogenotis ; the 

 wood-bundles in such stems are arranged in circles, each new circle being 

 deposited outside of the circle of last growth. Plants producing such 

 stems are called exogens. 



Stems like those of the Indian-corn and tulip are said to be endogenous. 

 The wood-bundles in such stems are not arranged in circles, but are devel- 

 oped irregularly throughout the stem. Plants producing such stems are 

 called endogens. 



£. The Arrangement of the Buds. 



25. Point out the position of the various buds on the 

 maple twigs. 



26. («) Observe the terminal bud and discover into 



what it is developing. 

 (3) Note the way in which the new leaves are 



arranged along the stem, 

 (c) Compare this arrangement with that of the 



leaves of other trees in the neighborhood, 



as the horse-chestnut, elm, basswood and 



beech. 



27. Observe the lateral buds on the stem of last year's 

 growth and discover what they will become. 



