BOTANY FOR BEGINNERS 



CHAP. 



EXPT. 36. Take a few Beans and soak them in water for twenty- 

 four hours. With a sharp knife cut longitudinal slices from the radicle 

 and place them on a glass slip, such as is used for microscope work. 

 Hold the glass slip between the eye and a strong light and place the 

 hand-lens up to the eye. Move the sections first 

 towards the lens and then away from it, until they 

 appear clear. Near the apex of the radicle a dark 

 inner portion and an outer lighter part can be 

 made out. The dark portion is the growing point, 

 and the lighter part the root-cap. 



The Primary Roots. The root pro- 

 duced by the elongation of the radicle is 

 termed a primary root. When the primary 

 root persists and continues to grow it is 

 called a tap-root. The Oak, Bean, and 

 Wallflower produce tap roots. Branches 

 are produced from the primary root in regu- 

 lar order, the oldest being found towards its 

 base, i.e., near the apex or growing point. 



The Secondary Roots. The lateral 

 branches of the primary root are termed 

 secondary roots. They differ from the 

 branches of the stem in not being produced 

 in the axil of leaves, nor from buds ; but they are formed in 

 regular order. Each plant produces a definite number of rows of 

 rootlets, which are arranged longitudinally, the roots in each row 

 being accurately one above the other. The secondary roots grow 

 horizontally or somewhat obliquely, not straight down like 

 primary roots, and in this way the roots between them parcel out 

 the soil. In the Wallflower there are four rows of roots, which 

 strike out north, south, east and west, and it is clear that 

 between them there is always unoccupied ground. This 

 unoccupied ground is worked by roots produced from secondary 

 roots and known as tertiary. They have no definite direction 

 of growth, but spread outwards, upwards, and in all directions, 

 thus reaching every part of the vacant soil. 



EXPT. 37. Obtain a Wallflower plant with perfect roots. Wash the 

 roots in water so as to remove the soil. 

 Examine the roots and observe 

 (i) The primary root. 



(ii) The secondary roots forming four rows, 

 (iii) The tertiary roots growing from the secondary roots. 



FIG. 70. A Mustard 

 seedling, showing 

 root - hairs and 

 cotyledons. 



