THE STEM 95 
for building and furnishing our houses that we get from the 
woody trunks of trees. When we think of all these things, 
it seems hardly possible to overestimate the importance of 
this part of the vegetable kingdom to man, or to exert 
ourselves too strenuously to regulate and prevent the de- 
struction of these invaluable natural resources. 
Practical Questions 
1. Would you judge from the observations made in the foregoing sec- 
tion, that the work of an organ determines its form, or that the form deter- 
mines its work? (99, 100, 108.) 
2. Which is the more important, form or function? 
3. Name some plants that are propagated by rootstocks; by runners 
or stolons; by rhizomes; by tubers; by bulbs. 
4, What is the advantage of propagating in this way over planting the 
seed? (104, 106.) 
5. Mention any other advantages that the various plants named may 
gain from the development of their underground parts. (104.) 
6. What makes the nut grass so troublesome to farmers in some parts 
of the country? 
7. Is its “nut” a root or a tuber? How can you tell? (106.) 
8. Suggest some ways for destroying weeds that are propagated in this 
way. 
9. Could you get rid of wild onions in a pasture by mowing them down? 
By digging them up? (107.) 
10. Is it wise for farmers to neglect the appearance of such a weed 
in their neighborhood, even though it does not infest their own land? 
11. Name any plants of your neighborhood, either wild or cultivated, 
that are valued for their rhizomes; for their tubers. 
12. What part of the plants named below do we use for food or other 
purposes? Ginger, angelica, ginseng, cassava, arrowroot, garlic, onion, 
sweet flag, iris, sweet potato, Cuba yam, artichoke. 
13. Why are the true roots of bulbous and rhizome-bearing plants 
generally so much smaller in proportion to the other parts than those of 
ordinary plants? (89, 104.) 
14. If the Canada thistle grows in your vicinity, examine the roots and 
see if there is anything about them that will help to account for its hardi- 
hood and persistency. 
15. If you live in the region of the horse nettle (Solanum Carolinense), 
explain how it is helped by its root system. (89.) 
