80 BOTANY 



Oxidation in the Human Body. — Exhale strongly through a straw or a 

 glass tube into limewater. The limewater turns milky, showing that 

 oxidation of organic matter has taken place within the body. 



If now a glass cylinder in which has been placed some moist blotting 

 paper on which a handful of soaked peas or beans are resting is left over- 

 night in a moderately warm room, and if the air within the jar is tested 

 the following morning, carbon dioxide will be found present. How shall 

 we explain its presence, in view of the above test with the human breath ? 



Experiment. — Place sawdust in each of two small boxes (cigar boxes will 

 do) and plant an equal number of bean, pea, and squash seeds in each. 

 Place one box in a warm room (in the winter near a radiator or stove), 

 the other in a room where the temperature will not exceed 70° Fahrenheit. 

 Be careful to give each box the same conditions of light and moisture. In 

 which box do seeds first germinate ? Which box shows the better growth 

 after three weeks have elapsed ? 



Moderate Temperature Best. — Another factor influencing the 

 germination of seeds is that of temperature. What is the most 

 favorable temperature for the germination of the bean, pea, and 

 squash f ^ From this experiment we find that although a high 

 temperature may stimulate the seed to immediate activity, never- 

 theless, later, the seeds in moderate temperature do better than 

 those in the heat. The temperature at which different seeds ger- 

 minate varies greatly. Those of you who have a garden at home 

 know that even some varieties of seeds germinate at lower temper- 

 atures than others of the same species; for example, early peas, 

 lettuce, or radish seed. As a general rule, increase in tempera- 

 ture is favorable up to a certain point, beyond which it is injuri- 

 ous to the young plant. Can you determine this danger point 

 from your experiments ? 



Light has a certain marked effect on young seedlings, which 

 will be considered when we take up the growth of the stem in 

 more detail. 



Selective Planting. — Although it has been noticed for a long time that 

 healthy seed usually produced healthy plants, it is only within recent years 

 that farmers have begun to appreciate what can be done by selective plant- 

 ing. By selective planting we mean choosing the best plants and planting the 

 seed from these plants with a view of increasing the yield. In doing this we must 

 not necessarily select the most perfect fruits or grains, but must select seeds 

 from the best plants. A wheat plant should be selected not from its yield 

 alone, but from its ability to stand disease and unfavorable conditions. 

 In 1862 a Mr. Fultz, of Pennsylvania, found three heads of beardless or bald 



^ See Hunter and Valentine, Manual, page 223. 



