12 BULLETIN 784, U. S. DEPAETMENT OP AGEICULTURE. 



basing their worth upon the points scored? Rating 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 1T5 bushels per acre ? 



LESSON VI. 



Subject. — The potato tuber (and plant) structure. 



Prohlem. — To understand methods of potato requirements for 

 growth. 



Sources of information. — Farmers' Bulletin 533; Department 

 Bulletin 176; bulletins from State college of agriculture. 



Illustrative inaterial. — 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. Wliat 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. Note 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 



