LABORATORY EXERCISES II 



Vm. The Mature Plant 



The root (Quercus alba) in cross section. Draw x$. Study the 

 details carefully with hand lens. Is there a central pith (medulla) ? 

 Medullary rays? Vessels or tracheae in the wood. How arranged? 

 Components of the bark? 



With scalpel and needles determine the texture of the various parts 

 of the root. 



Are the vessels true tubes ? Can you blow through them ? (Exp. 3 .) 

 Longitudinal section of root tips (microscope, prepared slide) . Note 

 the arrangement of the cells, and the root cap. 

 The stem (Quercus alba) (Aristolochia) in cross section. Draw X4. 

 a. One year old stem. b. Two year old stem. c. Three year 

 old stem. Note annual rings, medullary rays, epidermis, cork, 

 chlorophyll. Compare in the three sections, the pith, the wood 

 and the bark. What changes occur as the stem grows older? 

 A branch at least three years old. Can you determine from surface 

 appearance the limits of the i, 2 and 3 year old parts? How? Lo- 

 cate the limit of the last season's growth (the twig). 

 Draw the twig (white oak) showing the scale leaf scars, foliage leaf 

 scars, terminal and lateral buds. What is the function of these 

 buds? (see 48). Are there any branches? (see 48). 

 Study the growth of the preceding season. Are there any branches? 

 How old are they? Where do they occur? What determines the 

 position of a branch on a stem? 



How old is the basal portion of your branch? Determine by surface 

 inspection. 



Dissect a bud (Hicoria or ^Esculus). Note the character of the bud 

 scales and their arrangement. What is their funtion? What do 

 you find in the center of the bud? 



Structure of the stem (white oak). Study: a. cross, b. longitudinal 

 radial and c. longitudinal tangential sections of a block at least 

 eight years old. Note epidermis, cork, chlorophyll, other tissues 

 of the bark. What is the "grain" of wood? What are the flakes 

 in quartered oak? Why must the wood be "quartered?" 

 Compare the vessels of the root and stem. Compare roots and 

 stems of the same diameter with regard to rigidity. 

 Structure of the stem (corn), a. Study cross section of the corn 

 stem noting carefully the arrangement of the pith and vascular 

 bundles, b. Split the stem and draw. Are the vascular bundles 

 continuous? c. Set a section of stem in red ink (Exp. 4). Does 



