152 BOTANY: PRINCIPLES AND PROBLEMS 



470. When a branch is cut from a tree, the wound thus caused will 

 usually heal over. How does this healing take i^lace? 



471. If a branch is cut off very close to the trunk it will heal over 

 much more readily than if a stump is left projecting out some distance 

 beyond the trunk. Why? 



472. Why are rapidly growing plants tenderer than slowly growing 

 ones? 



473. Wliy do asparagus stalks become tougher and less desirable to 

 eat as they grow older? 



474. What is the best season to train woody vines upon trellises and 

 arbors or to fix the permanent shape of woody plants in other ways? 

 Why? 



475. Trees in exposed places are permanently bent in the direction 

 of the prevailing wind. Why? 



476. To develop large blossoms on a chrysanthemum plant, growers 

 cut off all flower buds but the terminal one. Why has this the effect 

 desired? 



477. If tobacco plants are "topped," (the upper part of the stem, 

 including the small leaves and the flower cluster being cut off when it 

 has begun to develop) the lower leaves on the stem, which are the valu- 

 able ones commercially, will grow larger than they otherwise would. 

 Explain. 



478. Which do you think will bear fruit first, a young seedling apple 

 tree or a scion of the same which has been grafted into a large tree? 

 Why? 



479. Why does a pruning of some of its roots often cause a tree to 

 bear more flowers and fruit? 



480. Why do many plants flower earlier if grown in pots than if grown 

 in the open soil? 



481. Why is it that apple trees, and many other northern fruit trees, 

 sometimes grow well in warm climates but never bear much fruit there? 



482. Why is a moist season good for forage crops but poor for seed 

 crops? 



483. In most plants which produce bulbs, it generally takes several 

 years before a plant raised from seed will begin to flower. Explain. 



484. Why does an apple tree usually bear a large crop only on alter- 

 nate years? 



