GROUP IV. SPERMATOPHYTES, SEED PLANTS. 
STUDY 16. 
A SEED PLANT. THE PINE. A Gymnosperm. 
A. The Vegetative Shoot. 
1. The cause of roughness on the main stem is leaf 
scales. What is their arrangement and what is 
found growing in the distal angle of some of 
them? What is the meaning of the occasional 
zones of scales ? 
2. The leaves are borne on small (dwarf) branches. 
What protection is there at their bases? How do 
young and mature leaves differ? What is the 
number, position, and arrangement of the leaves 
on a dwarf branch ? 
3. What is the general form of an entire leaf, also that of 
a cross-section? With m. find the stomates and ob- 
serve their abundance, location, and arrangement. 
Make a drawing of a dwarf branch and its leaves. 
With l.p. study a cross-section of a leaf. Observe 
the epidermis, mesophyl (green tissue) containing 
scattered resin ducts, and in the center a vein hav- 
ing two inclosed vascular bundles. Make drawing. 
6. With m. study a cross-section of a two- or three- 
year-old stem. Observe the pith, wood, and in- 
cluded medullary rays, and the bark which contains 
resin ducts in its green (middle) layer. What is 
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