340 GENERAL SCIENCE 



Carefully remove some of the outer shell from the larger 

 end of the egg, but do not injure the tough membrane 

 just inside the shell or the contents of the egg will flow 

 out. Now fasten the egg so that the larger end is in water 

 and the glass tube standing vertically. After a few hours 

 the white of the egg will be forced up the tube by the 

 water flowing through the membrane at the bottom, the 

 greater flow being toward the denser liquid. 



The general direction of roots is downward; but, like 

 the tops of plants, they send out branches which grow 

 sideways and sometimes just beneath the surface of the 

 soil. These branch roots send out other branches which 

 may grow either up or down or sideways. They will not 

 grow up out of the soil, but they grow close to the surface 

 where they can get abundant dissolved food. Many roots 

 of corn run horizontally close to the surface. There 

 are three things which determine or influence the direction 

 in which roots grow: (i) Force of gravity tends to cause 

 roots to grow downward. (2) Roots grow most rapidly 

 where there is abundant food, because they receive more 

 nourishment. (3) Water influences the direction of 

 growth. If the soil is dry, the deeper roots will grow 

 because they have a food supply. If the soil is excessively 

 wet, the surface roots will grow, and the deeper roots will 

 turn upward or to a horizontal position to keep out of 

 the water; for this reason the soil should be well drained 

 to permit the roots to go deeper and thus have a larger 

 feeding area and also sufficient water when a dry season 

 comes. If the roots are all near the surface, plants suffer 

 for want of water during a dry season. 



235. Stem. Recall the part of the young plant in 

 the seeds and grains which, during germination, grew and 

 formed the stem or the part of a plant above the ground. 



