294 Examination of the Matured Framework [BOOK n. 



Mohl, for ever going back to exact observation, was cutting away 

 the ground from under ill-considered theories in careful mono- 

 graphs, and at the same time bringing to light a mass of well- 

 established facts leading to further and serious investigation. 

 These theories have now only a certain historical interest, while 

 von Mohl's contemporaneous works are still a rich repertory of 

 useful observations, and true models of clear exposition. 



His written productions were preceded by a careful study of 

 all_branchesj)f botanical knowledge and the auxiliary sciences. 

 That he not merely acquired knowledge in this way, but 

 trained the powers of his understanding also, is shown by 

 the striking precision and clearness of his account of his first 

 investigations. At a time when the nature-philosophy and 

 Goethe's doctrine of metamorphosis in a distorted form were 

 still flourishing, von Mohl in spite of his youth approached the 

 subjects of his investigation with a calmness and a freedom 

 from prepossessions, which are the more remarkable when we 

 observe that his friend Unger was at first quite carried away 

 by the stream, and only slowly managed to reach the firm 

 ground of genuine inductive enquiry. 



Owing to the extravagances and aberrations with which he 

 made acquaintance as a young man in the nature-philosophy, 

 von Mohl contracted an aversion to all philosophy, evidently 

 taking the formless outgrowths from the doctrines of Schelling 

 and Hegel for something inseparable from it, as we may gather 

 from his address at the opening of the faculty of natural history 

 in Tubingen, which had been separated at his instance from 

 that of philosophy. His dislike to the abstractions of phi- 

 losophy was evidently connected with his distaste for far- 

 reaching combinations and comprehensive theories, even 

 where they are the result of careful conclusions from exact 

 observations. Von Mohl was usually satisfied with the establish- 

 ment of separate facts, and in his speculative conclusions he 

 kept as closely as possible to what he had actually seen, for 

 instance, in his theory of the thickening of cell-walls ; and 



