12 BULLETIN 784, U. S. DEPARTMENT OF AGRICULTURE. 
basing their worth upon the points scored ? Eating in this manner, 
what would be the loss at current market prices, on a 10-acre crop 
of each variety scored if the yield was 175 bushels per acre? 
LESSON VI. 
Subject. — The potato tuber (and plant) structure. 
Problem. — To understand methods of potato requirements for 
growth. 
Sources of information. — Farmers' Bulletin 533; Department 
Bulletin 176; bulletins from State "ollege of agriculture. 
Illustrative material, — Potato tuber specimens. The entire plant 
showing roots and clinging tubers. Obtain, if possible, entire plant 
of the tomato, tobacco, and jimson weed and other relatives of the 
potato. If plants are not obtainable, a diagram showing the potato 
plant as a whole will be found useful. Pictures of the related plants 
will be found in publications and may be used also. Charts may be 
used to show structure of the tuber and to illustrate types in connec- 
tion with such specimens as may be obtained. 
Class exercise. — The potato plant. Discuss with the class the fol- 
lowing topics: 
1. The potato-plant family, cultivated members, nature of some 
of the wild relatives. 
2. "What resemblances do you note between the tomato and the 
potato? Compare the fruit of the potato with the fruit of the 
tomato. 
3. Make a study of the stem, branching flowers, and seed balls. 
4. Xote differences in the plants and flowers of different kinds of 
potatoes. 
5. Why do not all varieties of potatoes produce fruit? 
6. The tuber : Note arrangement of eyes upon the tuber and trace 
their relationship to buds. Distinguish clearly between seed pota- 
toes and the real seed produced in the fruit. 
7. Study the root system of the plant and note the relation of the 
new tubers to the seed tuber. 
8. Cut the potato tuber into sections and note its different parts. 
9. "What resemblance can you find between the structure of a tuber 
and the structure of the green stem of a plant ? 
Practical exercises. — Students should be required as far as pos- 
sible to study the complete plant of the potato and related plants. 
The characteristics of the plant should be noted and comparisons 
made between the different varieties of potatoes. Contrasting 
studies of the potato and related plants should be made. It should be 
clearly shown that the tuber is an underground stem and not a root. 
Cross and longitudinal sections of the tuber should be made and the 
