THE COMMON BEAN il 



some time after emerging. By this behaviour the delicate 

 leaves of the plumule are protected from injury during their 

 progress upwards when a seed is sown in earth or sand. 



Ex. 3. — Fold up some soaked beans in two thicknesses of white flannel 

 made damp, and place them on a plate. Cover them with another plate 

 placed upside down, and leave them in a warm room. Examine them twice 

 a day, leaving them exposed to the fresh air for a few minutes each time, 

 and keeping the flannel damp, not wet. When they sprout notice the place 

 where the radicle has come out of the seed-coat. Let some grow till the 

 radicle and plumule are well out of the seed, and compare the various parts 

 of the sprouted seeds with unsprouted ones. 



2. Germination. — When the pod of the bean is developing, the 

 embryo in the seed is being fed by the parent and visibly grows 

 until ripeness is attained. The young plant then assumes a dor- 

 mant or resting state within the seed without showing any signs 

 of life. Under certain conditions, however, the plantlet begins 

 to wake up, and soon escapes from its protective coat to lead 

 a separate and independent life. This awakening from a resting 

 condition to a state of active growth is called germination, and 

 is dependent upon an adequate supply of (i) water, (2) heat, 

 and (3) air or oxygen. It is also essential, of course, that the 

 plantlet in the seed must be alive. 



The exact nature of the dormant state of seeds is not 

 understood, but in old seeds and those which are gathered 

 in an immature condition or badly stored the embryo is often 

 weakened or actually dead ; in the latter case no germina- 

 tion is possible. The exact length of time which seeds may 

 be kept before death of the embryo takes place has never 

 been satisfactorily determined; it varies with the species 

 of the seed, its ripeness and composition, and also with the 

 method of storage. In the case of most farm and garden seeds 

 kept in the ordinary way, few of them are found capable of growth 

 after ten years, and a large number die in two or three years, but 

 on this point more will be said in a later chapter. For present 

 purposes it will suffice merely to mention that age is a deter- 



