342 APPENDIX 



pensive equipment may be substituted. Student lamp chimneys 

 may be used to replace glass tubes in Ex. 8 and 14. Tin cans 

 with perforated bottoms may be used to replace the percolator 

 equipment in Ex. 9. The same cans may also be used in Ex. 

 11. Solid-bottom quart tin cans may be used to replace the 

 equipment called for in Ex. 10. In Ex. 13 four-gallon crocks may 

 be used to replace the soil cylinders. If crocks are used to replace 

 the evaporation cylinders, the soil must be saturated with water by 

 applying water at the top before the mulches are added. 



Four types of soil are needed in the laboratory : gravel, sand, 

 loam, and clay. The gravel and sand may be obtained along 

 streams, or if no stream is convenient, it can be secured as concrete 

 sand from local lumber dealers. The concrete sand should be sifted 

 through a sieve twelve meshes to the linear inch. The coarser 

 material will furnish gravel and the finer material sand. Loam 

 and clay can usually be obtained near the school. All the soils 

 should be thoroughly air dry, pulverized, and sifted before they 

 are used. 



Crops. The laboratory exercises in crops require head samples 

 and seeds of a number of the common cereals and legumes. It will 

 be necessary for the instructor to secure samples of heads of the 

 grains to be studied. This can best be done by collecting the ma- 

 terial in the field. If field samples have not been secured, it 

 may be possible to obtain them from stacks or barns where this 

 material has been stored. Samples of threshed and shelled grain 

 may be obtained from local mills and elevators. Some of the more 

 uncommon grains and seeds can be secured from seed houses. 



Type Samples. It is impossible successfully to study types 

 and classes of grain without using a standard for comparison. 

 It may be possible for schools to obtain type samples of grains from 

 their state agricultural experiment stations. The authors of this 

 manual, realizing the difficulty that many schools will have in obtain- 

 ing suitable type samples, have arranged to supply this material 

 at a cost of 50 cents per case of six samples or $3.50 for an entire 

 set of 48 samples. (This price does not include postage or express.) 

 These samples will be put up in glass-front cases, properly labeled, 

 and will include type samples of wheat, oats, rye, barley, legumes, 

 and grass seeds. 



