Seeds and How They Grow 511 



Selecting and Testing Seeds. Many seeds lose their ability 

 to sprout when kept too long. Other seeds may fail to germinate 

 for other reasons. Consequently, many farmers and gardeners 

 select and test seeds carefully before planting them. 



Here is a simple way to test seeds. Place several layers of 

 blotting paper in a dish. Scatter the seeds to be tested over the 

 paper. Cover the dish to reduce evaporation and set it in a warm 

 place. Examine the seeds at intervals until sure that all have had 

 a chance to germinate. Then find the per cent of the total seeds 

 that have sprouted. By testing seeds from several other sources 

 and comparing the results, the best seeds for planting can be 

 determined. 



Experiments with Roots and Stems. 



To Show the Response of Roots to Gravity. That roots 

 will grow in a downward direction may be shown by planting 

 clover or other small seeds in a small glass container, and by 

 tipping it at different angles from time to time as the roots develop. 

 In whatever position it is placed, at a slant or even upside down, 

 the roots will gradually turn downward. This is caused by the 

 attraction of the earth, known as gravity. This response to 

 gravity is positive when objects tend toward the center of the earth 

 and negative when they tend away from it. It is positive with 

 respect to roots, but negative with respect to stems. Stems which 

 naturally grow upward cannot be made to grow downward. 



To Show the Response of Roots to Moisture. The effect 

 of the presence of moisture near roots may be illustrated by 

 planting soaked seeds near the center of the top of a glass box 

 filled with sawdust which has been moistened in one end of the 

 box and not moistened in the other end. The tiny roots will grow 

 downward and turn towards the moist part. This tendency is 

 very beneficial to plant growth, especially in sections where a lack 

 of sufficient moisture prevails. This attraction of roots toward 

 moisture accounts for the fact that drains sometimes become 

 clogged with roots of willows, grasses, and other plants. 



To Show the Response of Stems and Leaves to Light. 

 Place small growing plants in a window, well exposed to the sun 

 and notice that the stems and leaves tend to turn so as to secure 



