8 SEEDS : STRUCTURE AND GERMINATION 



passes from the parent to enable the young seed to develop. At 

 first the pod exists in a rudimentary form in the centre of a flower, 

 and its parts and contents are very small; they are nevertheless 

 readily seen with a pocket lens. After the fading of the flower, 

 the pod and seeds within it grow larger and larger at the expense 

 of food supplied by the rest of the plant, and ultimately when 

 ripe the funicles wither and dry up, and the seeds become de- 

 tached from the parent which has produced them. 



When dry and ripe each bean seed is hard, with an uneven 

 surface, but its internal construction cannot be clearly examined 

 in this condition. On soaking in water for twelve hours, 

 however, it becomes softer, and the parts can then be easily 

 investigated. 



The outside, which is a pale buff colour, is smooth, and has at 

 one end a narrow elongated black scar called the hilum of the 

 seed. It is known popularly as the ' eye ' of the bean, and marks 

 the place where the broad end of the funicle separated from the 

 seed when it ripened in the pod. 



Quite close to one end of the hilum is a very minute hole 

 known as the micropyle, easily seen with a lens, and through 

 which water oozes out usually accompanied by bubbles of air 



when soaked beans 

 are squeezed be- 

 "C tween the finger and 

 thumb. This open- 

 ing communicates 

 with the interior of 

 the seed, and is the 

 only one it possesses. 



FlG.3.-ThesameasFig.2, Qu sHtting rOUnd 



after removal of one coty- o 



ledon ; r radicle; 3 the the edffc with a knife, 



plumule ; c cotyledon of ° ' 



embryo. thc outcr part of the 



bean can be stripped off as a pale, semi-transparent, leathery 

 membrane; this is known as the testa or seed-coat, and is thickest 



Fig. 2. — Bean embryo, show- 

 ing (r) radicle and (c) 

 cotyledon. 



