282 PRINCIPLES OF PLANT CULTURE 



Seed vitality limited by age (164). Test seeds of 

 lettuce, parsnip, onion, etc., 1 year, 2 years and 5 years 

 old, respectively. 



Stratification of seeds (169). Perform the process, 

 as described, in boxes or large flower pots. 



Sun-scald (185). Require each student to make a 

 lath tree protector (Fig. 59). 



Winter protection of plants (201). Protect half- 

 hardy shrubs by wrapping them with straw or covering 

 them with earth. 



Foretelling frost (206) . Devote an exercise to the 

 use of the psychrometer and the computation of the 

 dew point. 



Plant protectors (278) . Require each student to 

 make at least one plant protector, as shown in Fig. 67, 

 patterns for which are to be furnished. 



Kerosene emulsion (294) . Let each student make a 

 given quantity of the kerosene emulsion after one of the 

 formulae given. 



Spraying pumps (304) . Give at least one exercise to 

 the construction and use of spraying pumps and nozzles. 



Prevention of grain smuts (325) . Require the stu- 

 dents to treat a quantity of oats with formalin as de- 

 scribed. 



Bordeaux mixture (329) . Require each student to 

 make a stated quantity of the bordeaux mixture after 

 the formulae given. The better mechanical quality of 

 the freshly prepared mixture can be determined as follows. 

 Prepare a sample of the mixture and allow it to stand some 

 time, e.g., a day or a week, and settle. Prepare a fresh 

 sample, then shake both up and allow them to stand side 

 by side in tall glass jars or bottles and compare the rate 

 of settling. A similar comparison may be made as to 



