56 SOIL AN IMPORTANT FACTOR 



Sulfur enters into the composition of protein. 



Magnesium seems particularly necessary for leaf development. 



Iron is necessary for chlorophyll formation. 



THE FRUITION PERIOD 



During this period the plant arrives at its maturity. It 

 reaches its object of life; viz., the production of fruit or seed to 

 propagate itself. During this period grains "fill" and harden, 

 and fruits mature and ripen. This is not a period of food manu- 

 facture, but rather of translocation of foods from the stems and 

 leaves to the fruit or seed. Air, moisture and favorable tempera- 

 ture are the necessary requirements. 



Demonstrations. Material Needed (not including demonstration No. 8). 

 About 12 ounces of corn (seed) ; a few wheat kernels, and a few clover, cucum- 

 ber, oat and bean seeds; 6 tumblers; 1 balance; a tablespoonful or more of 

 salt; 1 quart of quartz sand; 6 one-gallon crocks; 18 quarts of loam, or silt 

 loam; and 10 quarts each of rich garden soil and a poor soil of the same class. 



To Show That Seeds Absorb Much Water Before They Germinate. 

 Procedure. Weigh out 50 grams or 2 ounces of either corn, beans or small 

 grain and soak in water for 24 hours. Then wipe off the adhering water and 

 weigh again. Determine the per cent of water absorbed. (Use weight of dry 

 seeds as basis.) 



To Show That Temperature Affects the Rate at Which Water is Absorbed 

 by Dry Seeds. Procedure. Weigh out two lots of seed of 50 grams or 2 ounces 

 each. Soak one lot in warm water and the other lot in cold water for about 

 two hours. Wipe off the adhering water, weigh, and determine the per cent 

 of water absorbed. 



To Show that Salt Retards the Rate of Absorption of Water by Seeds. 

 Procedure. Place one 2-ounce lot of seed corn in fresh tap water, and another 

 lot in a strong salt solution. Keep all at the same temperature for several 

 hours. Then wipe the seeds and compare weights. 



To Show That no Added or Outside Plant-food Elements are Needed for 

 Germination. Procedure. Plant large, medium and small seeds (corn, wheat, 

 clover) in pure quartz sand. Keep moist with pure water. Keep in favorable 

 temperature, light, etc., and note time in which plants appear. Continue 

 observations until plants die. 



Questions. (a) Name the essential conditions for germination. 



(6) Why are not plant-food elements from outside sources needed for 

 germination? 



(c) Why do the lower leaves dry up first? 



(d) Will the dry material of the dead plants (roots and all) weigh more 

 or less than that of the seeds? Why? 



(e) Will the amount of ash be greater or less? Why? 



To Show the Effect of Temperature on Plant Growth. Procedure. Plant 

 either winter wheat or oats and cucumber seeds in each of two one-gallon 

 crocks filled with loam or silt loam. Place both jars in a favorable place. 

 Water. When the plants are well started, place one crock in a well-lighted 

 place having a temperature between 35 and 40 F. and leave the other jar 

 in the greenhouse under favorable temperature conditions. Observe results 

 after 10 days or two weeks. 



