165 



a cylindrical or conical surface. There is no question about such 

 i tuple connections between the internal structure of crystals and 

 u phenomena of phyllotaxis, as suspected by the Russian scientist, 

 le essential difference between the two cases remains this, that 

 11 kinds of net-planes can, with a greater or smaller probability 

 of occurrence, have the function of crystal-facets, while of all theore- 

 tically possible regular distributions of the loci of leaf-attachment 

 plants only those are realised by nature, whose divergencies 

 ipproach closely to those expressed by the fractions of the principal 

 ;ries indicated in the above, or of series deduced from it in a 

 simple way. 



