CHAPTER III. 



ROOT GEOTROPISM TISSUES VASCULAR CYLINDER 

 M ERISTEM ROOT-CAP. 



IN a bean-seed which has not begun to grow, the radicle 

 lies in the plane of the cotyledons and points towards the 

 micropyle. If a bean is sown (i.e. placed in damp soil) 

 with the micropyle downwards and the plane of the 

 cotyledons vertical (fig. 4 c), the radicle will grow straight 

 on in the direction in which it naturally points: but if 

 the bean is allowed to germinate lying on its side with 

 the plane of the cotyledons horizontal, this will not 

 happen, the radicle will bend at right angles to itself until 

 it points vertically downwards, and will then continue to 

 grow in that line as shown in fig. 12. In fact, in whatever 



FIQ. 12. 



GERMINATING BEAN. 

 The radicle (R) has curved geotropically downwards : fl", the hilum. 



D. E. B. 3 



