152 TYPE STUDIES 



2. The very numerous dwarf branches, each bearing a chister 

 (fascicle) of two, three, or more needle-like leaves, accord- 

 ing to the species studied. 



3. The thin scales on the dwarf branches wrapped around 

 the base of the cluster of needle leaves. Are these scales 

 morphologically leaves ? Why ? 



4. The bases of old scales spirally arranged, and covering 

 the main branches from the axils of which the dwarf 

 branches arise. Younger full-sized scales at the tips of 

 the shoots. What are these scales morphologically? 



5. The bud scales, or leaves, enveloping the terminal bud. 

 Illustrate these features in habit sketches. How many 



forms of leaves are there on the pine? 



6. On a branch two feet or more in length note the regions 

 that indicate the beginnings of one year's growth and the 

 end of another's. Draw such a region and explain the 

 peculiar arrangement of the scales iipon it. 



7. Observe the position of cones on the branches. How 

 many sizes do you find and what are their ages as shown 

 by their positions ? 



8. Note the branch scars on older portions of the stem and 

 main branches. 



B. The cell structure, or histology, of the stem. Cut cross sections of a 

 three- or four-year-old branch. These may be stained with advantage 

 (Sec. 212) and mounted in balsam. 



1. Observe under l.p. : (a) the restricted region of pith; (b) the layers 

 or rings of wood, or xylem, around the pith (what is the significance 

 of their number ?) ; (c) a layer of bast or phloem outside of the wood 

 and separated from it by a thin cambium ; (d) the outer bark coip- 

 posed of larger cells, in places green, but on the exterior dead 

 and forming scales ; (e) medullary rays appearing as radiating lines 

 running through the wood and bast ; (/) resin ducts in the wood 

 and outer bark. Are the medullary rays of the same length ? Do 

 any of them penetrate to the pith ? 



Show the position of these tissues in an outline sketch. 



2. Study the structure of the wood in the region between the growth 

 of two successive years. In a detailed figure show the form of the 



