138 PRACTICAL COURSE IN BOTANY 
angle, for instance, which a twig makes with its bough has a 
great effect in shaping the contour of the tree. Compare in 
this respect the elm and hackberry ; 
the tulip tree and willow; ashand hick- 
ory. Asageneral thing, acute angles 
produce slender, flowing effects; right 
or obtuse angles, more bold and rugged 
outlines. 
Practical Questions 
1. Has the arrangement of leaves on a twig 
anything to do with the way a tree is branched? 
(145, 151, 152.) 
2. Why do most large trees tend to assume 
Fie. 158.— Winter spray the excurrent, or axial, mode of growth if let 
a alone? (150, 154.) 
3. If you wished to alter the mode of growth, or to produce what nur- 
serymen call a low-headed tree, how would you prune it? (152, 153.) 
4, Would you top a timber tree? (152, 153.) 
5. Are low-headed or tall trees best for an orchard? Why? 
6. Why is the growth of annuals generally indefinite? 
7. Name some trees of your neighborhood that are conspicuous for 
their graceful winter spray. 
8. Namesome that are characterized by sharpness and boldness of outline. 
9. Account for the peculiarities in each case. 
II. BUDS 
Mareriat. — Expanding leaf and flower buds in different stages of 
development; large ones show the parts best and should be used where 
attainable. Some good examples for the opposite arrangement are 
horse-chestnut, maple, lilac, ash; for the alternate: hickory, sweet gum, 
balsam poplar, beech, elm. Where material is scarce, the twigs used in the 
last section may be placed in water and kept till the buds begin to expand. 
155. Folding of the leaves. — Remove the scales from a 
bud of horse-chestnut nearly ready to open, and notice the 
manner in which the young leaves are folded. This is called 
vernation, or prefoliation, words meaning respectively ‘“ spring 
condition” and ‘ condition preceding the leaf.” Leaves 
are packed in the bud so as to occupy the least space possible, 
and in different plants they will be found folded in a great 
