LEAVES AND THEIR MODIFICATIONS. 53 
8. What is the origin and structure of the hairs? How 
do they differ? Why? 
9. Draw and designate all parts, showing the results of 
the study in (6), (7), and (8). 
10. How does the epidermis of the dorsal and ventral 
surfaces differ, especially with reference to stomates 
and hairs ? 
11. With l.p. and h.p. study a thin transverse section in 
the region of a vein. Study the form and struc- 
ture of the vein. Near which surface isit? Why? 
12. How do the green cells (mesophyl) differ as to form 
and arrangement? If elongated, vertically ar- 
ranged cells (palisades) are present, near which 
surface are they? Why? 
18. Are there small chambers (intercellular spaces) be- 
tween the cells? Ifso, what is their purpose? To 
what do they lead? Why? Makea drawing and 
designate the results of your study. 
B. Leaf Variations. 
1. In the material provided, find leaves without stipules, 
others without petioles (sessile), and others with 
their blades divided into wholly separate pieces 
(leaflets) ; such leaves are compound. Make draw- 
ings of attached leaves to show these forms. 
2. Study the specimens for variation in venation. Do 
the veins make a prominent net-work (netted 
venation), or are they mainly parallel (parallel 
venation)? 
8. Of the netted venation forms, do the main veins arise 
from the base (palmately netted), or do they arise 
from a midrib (pinnately netted)? Make drawings 
to show the forms of venation. 
