GENERAL CONCLUSIONS. 349 



tion of growth-energy comparable with that of the electro-magnetic 

 field. 



The curves plotted by Mr E. H. Hayes should thus represent the 

 fundamental shape of the leaf-sections, and the general equation 

 is definitely put forward as a mathematical definition of a " leaf " 

 outgrowth.* Such curves, if seen in sections, would not at first 

 be regarded as equivalent to circles, while closely packed members 

 approach under similar conditions the form of quasi-squares ; 

 the conducting tissue (vascular bundles) being orientated aroimd 

 a point described as the centre of construction. With the help 

 of these curves and data it now becomes possible to pass on to 

 the next phase of growth and study the phenomena of varying 

 rates of growth, and more especially the retarded growth -systems 

 and unilateral modes of distribution which clearly characterise the 

 growing-points of shoots and the formation of leaf-laminae as 

 studied in planes other than the transverse, which has so far alone 

 been considered. 



* Annals of Botany, vol. xviii., p. 227. 



