18 Elementary Principles of Agriculture 



for wheat, rye and oats. Corn required three days, 

 and tobacco six days. Sugar beets germinated in 

 twenty-two days when the temperature was 41 Fahr., 

 while, at 65 Fahr., germination commenced on the 

 third day. (See H 94, Temperature of Soils.) 



29. Germinating Seeds Need Air. Growing plants, 

 including germinating seeds, must have air. They use 

 the oxygen of the air, and we call it respiration, just as 

 we do in animals. While plants do not have lungs, they 

 absorb the oxygen of the air and give off carbon dioxid. 

 (But see U 48, Carbon Assimilation.) 



29a. To show that germinating seeds use the oxygen of the air, 

 take two large fruit jars with good rubber bands. Into one put noth- 

 ing. Into the other put a big handful of soaked seeds of corn or 

 peas. Screw the tops ori tightly and let stand for about twelve hours. 

 Then carefully remove the top from the empty jar and thrust a 

 lighted splinter down to near the bottom of the jar, noting the dura- 

 tion and brilliancy of the burning taper. The taper goes out after 

 a time, because the burning of the wood uses up the oxygen in the 

 jar. Now thrust a lighted paper into the jar with the germinating 

 seeds, noting if it burns as brightly as in the empty jar. It goes out 

 quickly because the germinating seeds have used up all the oxygen, 

 and that carbon dioxid is present' may be proven by lime-water 

 poured down the side of each jar. The empty one gives no result, 

 while the other will show a white band on the inside of the jar. This 

 is the test for carbon dioxid.* 



30. Not All Seeds Germinate. Seeds often fail to ger- 

 minate when given the proper conditions for germina- 

 tion. This may be due to one or more causes. They 

 may be too old; they may have been gathered when 

 immature; they may have become too dry, or frozen 

 when not sufficiently dry. Sometimes they become 



*Carbon dioxid, exhaled from the lungs of animals and bv germinating 

 seeds, is a gas formed by the union of two elements carbon and oxygen. Oxygen 

 is a gas forming a large part of the air; carbon is a solid familiar as charcoal, 

 which is crude carbon 



