ROOT 5 



We can now define a root and a shoot. A stem is an axis 

 which bears lateral members — the leaves— dissimilar to itself. 

 A stem together with its leaves constitutes a shoot. A shoot 

 terminates in a bud, and is usually the ascending portion 

 of the plant : at least, parts of it are generally green. Lastly, 

 the shoot bears the flowers. A root is an axis whifh cannot 

 produce leaves as lateral members of itself: consequently it 

 does not terminate in a bud.* A root can only produce as 

 lateral members branches like itself: as a rule it is a 

 descending axis, and has no green colouring-matter. 



THE ROOT. 



If we fix a germinating bean (or pea) in a bottle contain- 

 ing air which is saturated with moisture, in the manner shown 

 in fig. 3, when once the root has commenced to grow 

 straight, we can follow the method of growth. To accomplish 

 this, we make a number of transverse marks 

 in Indian ink at equal and short distances 

 along the root. After twenty -four hours' 

 growth it will be found that the distance be- 

 tween the consecutive marks remains, the 

 same, excepting near the tip of the root, 

 where the marks have become separated by 

 longer intervals. This shows that the root 

 increases in length by elongation which only 

 takes place in the region of its apex : conse- 

 quently, the youngest part of a root is that 

 which is nearest its apex, whereas the oldest Fig. 3. 



is that nearest its base. 



A short distance behind its apex (fig. 4 rx) the root has 

 a broad encircling band of fine silky hairs — root-hairs (rh). 

 As the root grows at its apex new root-hairs form constantly 

 behind the tip, which, of course, has been carried forward, so 

 that the youngest root-hairs are those nearest the tip. These 

 hairs live for a short time only, for they soon shrivel and peel 

 off, and therefore they are found solely on the young and 

 more terminal portions of a root. 



A root may bear branches structurally similar to itself. 

 These arise on the main root at points nearer to the root-. 



* It has a root-cap, which is not possessed by a stem. 



