i] AIR REQUIRED FOR GERMINATION ii 



have considerable bearings upon practice ; gardeners 

 know well that certain seeds must be sown " in heat " or 

 they will not start ; amongst farm crops, the seeds of 

 turnips and mangolds make very little progress if sown 

 before the land has got warmed up by the spring suns 

 and cultivation. 



The next indispensable factor in the germination of 

 seeds is the presence of air, and this may be illustrated 

 by one or two simple experiments. Put some mustard 

 seeds into a bottle, fill it completely with water and 

 stopper it, then let it stand in a warm place ; a few of 

 the seeds may " chit " because there is a little dissolved 

 air in the water, but they will stop at that and cease 

 to grow any further. Grease the stopper of a wide- 

 mouthed bottle holding about a pint, put in half an 

 ounce of mustard seeds and enough water to wet them 

 thoroughly, stopper up and set in a warm place as before, 

 but this time in the dark. In a few days the seeds will 

 germinate, and as there is some air in the bottle they 

 will continue to push for a few days before they come 

 to a pause and stop for lack of more air. Now see what 

 has happened to the air inside the bottle by taking out 

 the stopper and inserting a lighted taper. It goes out, 

 indicating that the oxygen of the original air has been 

 so far used up that a candle can no longer burn. Now 

 decant some of the air into a clean bottle and shake it 

 up with lime water : the lime water becomes milky, 

 indicating the presence of carbon dioxide or carbonic 

 acid. The germinating seeds have thus affected the air 

 with which they were enclosed, just as a burning candle 

 would do or a breathing animal ; oxygen has been used 

 up, and carbon dioxide has taken its place ; something, 

 in fact, in the seed has been burnt, i.e., combined with 

 the oxygen of the air to form carbon dioxide and water. 

 The identity of the process going on during germination 



