PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 253 



point of growth. Thus, in the formation of epidermal cells the 

 nucleus lies at first near the centre, but as the outer wall thickens, 

 the nucleus moves towards it, and remains closely applied to it 

 throughout its growth, after which the nucleus often moves into 

 another part of the cell (Fig. 114, A, B). That this is not due 

 simply to a movement of the nucleus towards the air and light is 

 beautifully shown in the coats of certain seeds, where the nucleus 



Fig. 114. — Position of the nuclei in growing plant-cells. [tiAKERLAXnT.] 

 A. Young epidermal cell of Lmula with central nucleus, before thickening of the membrane. 

 B. Three epidermal cells of Momtera, during the thickening of the outer wall. C. Cell from the 

 seed-coat of Scopulina during the thickening of the inner wall. D. E. Position of the nuclei dur- 

 ing the formation of branches in the root-hairs of the pea. 



moves not to the outer, but to the inner wall of the cell, and here 

 the thickening takes place (Fig. 114, C). The same position of the 

 nucleus is shown in the thickening of the walls of the guard-cells 

 of stomata, in the formation of the peristome of mosses, and in 

 many other cases. In the formation of root-hairs in the pea, the 

 primary outgrowth alwavs takes place from the immediate neighbour- 

 hood of the nucleus, which is carried outward and remains near the 

 tip of the growing hair (Fig. 114, D, E). The same is true of the 



