82 PRODUCTIVE FARMING 



often controlled by spraying with iron sulfate before the grain 

 begins to send up its stems. The principle involved in this 

 method is this: The leaves of most grain crops and grasses 

 are naturally protected by a coating of wax or "bloom" 

 which keeps off the chemical and prevents their injury. The 

 weeds when young are tender and not thus protected. Hence 

 the chemical may be made strong enough to kill many kinds 

 of weeds without killing grasses or grain crops. 



EXERCISE. Collecting Weed Specimens. In the fall of 

 the year a collection of weeds should be made by the student. 

 One set of the specimens should be kept at the school. They 

 may be dried by spreading out the plants between large 

 folded newspapers. Put the pile of papers and plants on 

 the floor; place over them a board and stone or other heavy 

 object. This pressure will drive the moisture from the plants 

 into the papers. Change the papers from day to day until 

 the plants feel quite dry. They may then be fastened to 

 sheets of paper or cardboard eleven by seventeen inches. 

 Find the names of the weeds from any one who knows them, 

 group them into annuals, biennials, and perennials. U. S. 

 Farmers' Bulletin 28 will be of much help in the study of 

 weeds. 



EXERCISE. Seed Collection. Let the pupils bring to 

 school in the fall such weed seeds as they can find upon the 

 known weeds. These may be carried in small papers or old 

 envelopes on which the name of the plant is written. These 

 may be transferred to small bottles as in Fig. 15, or to holes 

 in a seed board made like the one shown in Fig. 14. A col- 

 lection of farm and garden seeds should also be made for 

 the school to use. 



Common Weeds. An alphabetical list of some bad weeds, 

 with useful information regarding them is given in the table. 

 (A = annual, B= biennial, P = perennial.) (Adapted from 

 H. R. Cox, U. S. Department Agriculture.) 



