ORGANS AND SYSTEMS OF ORGANS. 



177 



system, the variations in size of the contiguous organs, and the 

 tension-effects of the leaf-trace bundles. 



The mechanical results of the morphological factors are the pre- 

 dominance of the normal series of divergences (limiting value: 



FIG. 104. Diagramatic representation of the transition from the alternating 

 two-ranked arrangement to the spiral arrangement caused by the diminution 

 in the size of the organs. (After Schwendener.) 



relation of the golden section, extreme and mean proportion. (See 

 above.) This phenomenon is, therefore, not purely morphological 

 (Schimper, A. Braun, Bravais) but mechanically-morphological ; 

 for it represents mechanical results associated with almost constantly 



