SPECIAL FUNCTIONS AND FORMS OF STEMS 93 
The student should notice that, while budding and grafting 
are described as modes of vegetative reproduction, their object 
is not to inerease the number of shrubs or trees in the garden or 
orchard. It is rather a means of propagating the desired kind 
of plant with certainty —for example, to secure a certain 
variety of fruit. This cannot be done merely by growing seed- 
ling trees, since every seedling grown from any valuable kind 
of apple or pear may differ from all the others of the same 
lot (fig. 163), and not one of them be worth cultivating. 
Grafting often succeeds on plants of different species,! as 
the peach on the plum, the apple on the pear, and the pear on 
the quince. Sometimes it succeeds between different genera! 
of the same family, as the tomato on the potato. 
Many technical details best learned from a practical horti- 
culturist are necessary in order to bud or graft successfully. 
PROBLEMS 
1. What common feature would you be likely to find in the structure 
of the stems of pickerel weeds, cat-tails, and rushes, and in the leafstalks 
of pond lilies and lotuses ? 
2. Large cacti in the deserts of the southwestern United States and 
Mexico are often cut open in order that their sap may be used for 
drinking water. Where did the plant get so much water? How could 
it have used the water? 
3. What common garden plants are reproduced by bulbs? Can any 
of these be grown from seeds? 
4. Do most kinds of plants grown from bulbs bloom early or late? 
To what two kinds of climate are such plants suited? Give examples, 
among both wild and cultivated plants, to illustrate your answer. 
5. Could more than one kind of scion be top-grafted on a single 
stock? Why do top-grafted trees, after they come into bearing, require 
more careful pruning than ungrafted trees? What kind of fruit will be 
borne by shoots that arise below a graft? 
6. Do bulbs planted in autumn freeze in winter? What are the best 
methods and times for the outdoor planting of bulbs in your locality? 
Should different plans be used for different kinds of bulbs ? 
1 For the definition of the terms species, genus, and family, see Chapter XIII. 
