^eo LECTURE XXVII. 



axis or axis of growth which divides the entire figure symmetrically in both cases. 

 The Unes q q, on the other hand, are intended to show the boundary between two 

 different forms of growth in the given cell-network. In the cells lying beneath 

 qSg growth has taken place as in the growing-point considered above; the lines 

 yy, h h form confocal parabolas. On the other hand, the growth above the line qSq 

 has taken place as it was formerly supposed to do — namely, the growth in length 

 has here been most vigorous at the apex. It is at once obvious that in this way an 

 entirely different cell-network arises, and that the periclines and anticlines assume 

 quite other directions than at the apex of an ordinary growing-point. In the case of 



the latter, the pieces \^b and B, intercalated between the periclines, become shorter 

 in the given direction ; above the line q q, on the contrary, the pieces ire eE, inter- 

 calated between the periclines, increase in length in the order given. 



The state of affairs arbitrarily constructed in this scheme, however, is found 

 as a matter of fact in many roots of vascular plants, as shown in Fig. 287. The 

 growing-point of the root, the outline of which is here indicated by the line KKK, 

 presents the cell-network as in our scheme Fig. 284, and accordingly as in the portion 

 situated below qSq m Fig. 286. On the other hand, the mass of tissue marked by 

 the outline hhh'\% the root-cap, and it is at once perceived that this corresponds 

 with that mode of growth which is represented in Fig. 286 above the line qSq. 



