THE COMMON BEAN 15 



minating bean point to the conclusion that it is a living structure 

 and like an animal dependent on a proper supply of water, heat 

 and air for the manifestation of its life, but the parts of a young 

 bean plant after emerging from the seed soon give evidence of 

 the possession of peculiarities which are associated with life. 

 When put in the ground, the radicle, in coming out of the seed, 

 turns straight downwards and continues to grow in this direction. 

 This is the case no matter in what position the seed is placed. 

 If, after germination has commenced, it is taken and replanted 

 with the primary root pointing to the surface of the soil, the tip 

 of the root soon begins to curve downwards again, and will 

 maintain this course until again disturbed. 



The plumule behaves in exactly the opposite manner ; after 

 emerging from the seed-coat its bent tip grows upwards and 

 away from the root; if the seed is reversed and replanted the 

 plumule begins to curve in such a manner that its tip is driven 

 upwards towards the surface of the ground. That these peculi- 

 arities are somehow connected with life is clear, as dead embryos 

 show no such behaviour. 



Ex. 9. — Sow soaked beans in a flower pot or box filled with ordinary garden 

 soil placing them in various positions in it, some laid on the flat side, some 

 with the hilum directed upwards, and others with the hilum downwards. 

 Allow them to grow in a warm place : take them up as soon as signs of germin- 

 ation are noticed, and observe the direction the root and shoot have taken. 



The peculiar tendency for the root always to go downwards and stem 

 upwards can be investigated by sowing beans in ordinary garden soil and 

 afterwards reversing them. To avoid error all should be taken up, and 

 then placed again in the soil- in various positions — some as they were, a 

 few with their roots and stems reversed, and others laid in a horizontal 

 position. They may be re-examined at the end of a week. 



Another method of showing the same peculiarity may be carried out 

 thus: — Germinate soaked beans in damp flannel as in Ex. 3. When the 

 roots have extended about half an inch take two seeds and suspend them by 

 means of thread side by side in a bottle with their roots downwards and stem 

 upwards. The bottle should contain a little water to keep the air damp. 

 When the roots have grown about two inches reverse one of the seeds so that 

 its root points upwards and stem downwards. Notice that the tip of the 



