28 THE OAK 



and other peculiarities ; and if we could take a trans- 

 verse section exactly at this place we should see no 

 differentiation into axial cylinder and root-cortex, &c. 

 the small circular mass would consist of cells all 

 alike, and with very thin walls and full of dense proto- 

 plasm. This undifferentiated formative tissue is called 

 the embryonic tissue of the root (fig. 6, m). A little 

 behind this we see the axis-cylinder and root-cortex 

 already formed ; still further away we see the vascular 

 bundles appearing, first as very thin cords, and then 

 getting stronger and stronger as we recede from the tip 

 (fig. 6, pli and x) ; and similarly we trace the gradual 

 development of the other parts in acropetal succession 

 i.e. the nearer we go to the apex the younger the parts 

 are. 



Now, there is a conclusion of some importance to be 

 drawn from the putting together of these facts namely, 

 that all the structures found between the embryonic 

 tissue at the tip of the root and the place where the root 

 joins the stem have been gradually formed from the 

 embryonic tissue in acropetal succession. We may 

 picture this by marking a given level on the root, 

 some distance away from the tip, where the axis-cylinder 

 is sharply marked and has well developed vascular bun- 

 dles, the root-cortex is distinct, and the piliferous layer 

 bears root-hairs, and remembering that so many days or 

 weeks ago this very spot was in the then growing-point, 

 and consisted of embryonic tissue with the cells all alike. 

 Or we may put it in a different way thus : the present 



