RELATIONSHIPS OF SYMMETRY 1 



i. 



INTRODUCTION. 



BY the expression 'relationships of symmetry' we understand here the 

 general relationships in space of the configuration of plants. The plant- 

 body is seldom developed equally in all directions of space, although 

 this is the case or appears to be so in the monergic spherical cells of 

 Eremosphaera ; the construction is usually different in different directions. 

 The investigation of the relationships of symmetry is of great importance, 

 because they stand in the closest connexion with life-phenomena and 

 are also of considerable significance for the formation of a critical estimate 

 of the whole construction of the plant. The ' spiral theory,' which for 

 so many years dominated morphology and frequently led into blind 

 alleys, was founded essentially upon an incorrect generalization regarding 

 the relationships of symmetry of orthotropous shoots of the higher 

 plants. 



We must first of all recall here, what was explained in the preceding 

 section, that most plants and parts of plants show a polar construction, 

 an opposition between apex and base an opposition which is seen indeed 

 in many cell-colonies, but which is only sharply marked when a vegetative 

 point comes into existence, because with its appearance the polarity is 

 impressed on parts from their beginning. We have seen that its pheno- 

 mena are well marked in the regeneration of many parts of plants. In 

 normal life the different construction of an apical and a basal region 

 is very conspicuous, particularly in trees and shrubs.. We notice in these 



1 See Von Mohl, Uber die Symmetrieverhaltnisse der Pflanzen, Vermischte Schriften, 1845; 

 Herbert Spencer, Principles of Biology, ii. ; Sachs, Lehrbuch der Botanik ; Id. Uber orthotrope 

 und plagiotrope Pflanzenteile, Arb. d. bot. Instituts in Wiirzburg, ii. p. 226; Id., Gesammelte 

 Abhandlungen, ii. ; Goebel, Uber die Verzweigung dorsiventraler Sprosse, in Arb. des bot. Instituts 

 in Wiirzburg, ii. p. 353 ; Id., Vergleichende Entwicklungsgeschichte der Pflanzenorgane, p. 141. 

 GOEBEI, F 



