General Introduction 19 



conclusions. His theories were not always sound, and his 

 judgement was sometimes subordinated to his enthusiasm. 

 For example, he gave in his adhesion unreservedly and 

 prematurely to Naegeli's theory of the constitution of 

 organized structures, and attributed finality to it. But 

 its downfall, or at any rate its very drastic modification, 

 was only distant about twenty years. Sachs' theories 

 have already passed out of the normal field of view, while 

 Darwin's grand generalization stands unchallenged. Darwin 

 had the philosophic mind, combined with the unwearied 

 patience of the true student of Nature and the explorer of 

 her secrets. 



Still the two great figures stand as dominating botanical 

 science at the opening of our period, and under the great 

 influence of both the stream of thought has been widened 

 and deepened, and from the semi-obscurity of the first 

 half of the century we have advanced to the relatively 

 brilliant light of the present day. 



It has been especially in the study of physiology that 

 the greatest progress has been made, though incidentally 

 all sections of the science have been materially advanced. 

 The idea of the struggle for existence carried on continuously 

 by the plant, directed attention to its equipment and led 

 at once to the recognition of its power of appreciating changes 

 in its environment. Linnaeus had denied the existence of 

 the power of feeling in the vegetable organism, making it 

 one of the points of difference between animal and plant. 

 Already a certain hesitation in accepting that dictum had 

 been felt by many botanists ; from this period it disappeared. 

 The nature of living substance was and had been only 

 imperfectly appreciated, though von Mohl had made some 

 investigations in that direction. Now the protoplasm, to 

 use the name he gave it, assumed at once its proper impor- 

 tance, and its peculiarities formed the basis of the physio- 

 logical investigations at once initiated. The role played 



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