FORMS OF ROOTS 



63 



you will find the cortex to be very large, the cells crowded 

 with starch grains, and the central cylinder, a small strand 

 in the middle, to contain four groups of wood alternating 

 with four groups of bast. 



If a shoot, bearing axillary tubers, be placed in water for 



Fig. 28. Development of Tubers in the Lessek 

 Celandine. i, plant with tubers at successive nodes; 

 2, 3, 4, seedlings bearing axillary tubers ; 5, tuber 

 bursting through the leaf -sheath; 6, node with axillary 

 tubers, one bearing a leaf ; 7, ditto, with the two leaves 

 removed ; /, fruit ; I, foliage-leaf ; /, tuber ; r, root ; 

 sc, scale-leaf. 



a few days, leaves may be seen to arise from the axils of 

 scale-leaves at the bases of the tubers (Fig. 28, 6 and 7). 

 Tubers, therefore, are compound structures : the lower leaf- 

 bearing portion is a stem ; and the outer or distal part is 

 a root with a double function : (a) it absorbs by means of 

 root-hairs, and (b) stores up starch in the bulky cortex. 



