ANTICLINES AND PERICLINES IN THE GROWING-POINT. 



449 



below only reach the neighbourhood of the focus. In other words, the corresponding 

 cell-divisions only take place when the periclines beneath the centre of curvature have 

 become sufficiently far removed from one another for new periclines to be intercalated 

 between them ; and the same is true of the anticlines A a. It is easy to see on the 

 scheme, Fig. 284, that the curvatures of the construction-lines are particularly sharp 

 around the common focus of all the anticlines and periclines. 



Many hundreds of median longitudinal sections through growing-points of 

 shoots and roots, drawn by very different observers without even the most distant 

 perception of the fundamental principle, accord with the construction which I have 

 given, and demonstrate its accuracy; and, further, it may be said that all these 

 observations, have been made under the influence of t wo false premisses ; first, that 

 growth — i.e. increase in volume — takes place chiefly at the apex of the growing-point, 

 and secondly, that cell-divisions are an essential cause of growth. That the latter 

 is unfounded has already been insisted upon above, and I have shown clearly that 

 it is just the apical region of the growing-point which is that where growth is slowest 



FIG. sSs.— Longitudinal section through the growing-point of a winter-bud of Abies pectinata (X about zoo). 

 s apex of growing-point ; b b youngest leaves ; r cortex ; m pith. 



andincrease in volume least.__ The details of this, however, would here carry us too 

 far. It need only be mentioned that the mere consideration of the cell-network at 

 the growing-point and the course of the anticlines and periclines shows most 

 clearly that growth must be less active at the apex itself than at any point lying 

 further bacK It is only necessary to suppose that in the scheme (Fig. 284) growth 

 — i.e. the intercalation of mass — is more active in the neighbourhood of the focus] 

 of the anticlines and periclines than fiirther back, to see that, according to the 

 described laws, the cell-network must assume quite another form — i.e. the course 

 of the anticlines and periclines must be essentially different. 



Perhaps this important and formerly incorrectly apprehended relation will be 

 rendered sufficiently clear if we here again make use of an arbitrary construction. 

 We may assume that in Fig. 286 the lower figure represents a square surface 

 consisting of 36 cells, and, for the purpose of better guidance, the lines qq and vi are 

 drawn thicker. Let us now suppose that these 36 cells begin to grow as a whole, and 

 that the upper figure arises therefrom. The line vi then represents the longitudinal 



[3] Gg 



