CHAP, iv.] Metamorphosis and of tlie Spiral Theory. 167 



history of development and the mechanical forces concerned. 

 Again, it was a great and essential defect in the theory, that in 

 assuming the spiral arrangement it entirely neglected the 

 relations of symmetry of the plant-form, which are in many 

 cases clearly expressed, and their connection with the outer 

 world, on which Hugo von Mohl had already published some 

 excellent remarks in 1836, a defect, which unhappily is not 

 yet sufficiently appreciated. A due consideration of these 

 objections, and of the cases in which the history of develop- 

 ment is opposed to the constructions of the theory, must have 

 led to the conviction that the idea of a spiral tendency in the 

 growth of plants is at least not borne out in all cases, and 

 more profound reflexion would show, that a scientific prin- 

 ciple, really explaining the phenomena, is no more to be 

 found in the assumption of such a general tendency, than in 

 a like assumption with regard to the heavenly bodies, that 

 they have a tendency to elliptic movement because they com- 

 monly move in ellipses. Hence Hofmeister, the latest investi- 

 gator of the doctrine of phyllotaxis on the basis of the history 

 of development, comes to the conclusion that the notion of 

 a screw-shaped or spiral course of evolution of lateral members 

 of plants is not merely an unsuitable hypothesis, but an error. 

 Its unreserved abandonment is, he considers, the first con- 

 dition for attaining an insight into the proximate causes of the 

 varieties of relative position in the vegetable kingdom. But 

 this judgment, correct as it is, was pronounced thirty years 

 after the appearance of Schimper's theory; history, which 

 speaks from another point of view, and not only enquires into 

 the correctness of a theory but has to appraise its historical 

 importance, speaks in a less unfavourable manner. The chief 

 point here is not whether the theory was right, but how far it 

 contributed to the advance of the science. It was distinctly 

 fruitful in results, for it brought the important question of the 

 relative positions of organs for the first time into the front 

 rank in the study of morphology ; we may even say that a 



