12. 
18. 
14. 
15. 
16. 
be 
18. 
19. 
20. 
STEMS AND THEIR MODIFICATIONS. 49 
What is the relation of the branches to the leaf 
scars ? 
Make drawings showing the results of study from 
1 to 12 inclusive. 
Examine the cut ends of specimens which show 
bark, wood, and pith distinctly. Draw and desig- 
nate all parts. 
In a transversely cut end of a woody stem two or 
more years old, with m. endeavor to explain the 
cause of the rings found in the wood. The 
radial lines of the wood are called medullary 
(pith) rays. Where do they begin and termi- 
nate? Draw and name parts. 
In a thin cross-section of a young woody stem, 
with l.p. and h.p. note how the outer, middle, and 
inner layers of the bark compare in structure and 
color. What is the purpose of each? 
How do the cells of the wood and pith rays differ ? 
Make a drawing of a quadrant and designate its 
parts. 
In a cross-section of Corn, Asparagus, or Smilax 
compare the arrangement of its tissues with 
those already studied. Draw and name its 
parts. Plants with this type of stem are mono- 
cotyledons and those first studied are dicotyle- 
dons. 
In a longi-section of a woody stem and its branch 
trace the tissues of the branch to their origin in 
the stem. Make drawing to illustrate. 
In a longi-section of a stem and leaf stalk find the 
origin of the leaf tissues. On the basis of this 
study explain the “dots” found in some leaf 
scars, as in Buckeye and Sumach. 
E 
