CHAP, i.] Investigation of the fertilisation-process. 435 



Entstehung des Embryo der Phanerogamen,' Leipzig, 1849. 

 Tulasne also came forward in opposition to Schleiden's theory, 

 being thoroughly convinced that there was no actual contact of 

 the pollen-tube with the egg-cell, denying indeed the existence 

 of the egg-cell before fertilisation. Thus a vehement contro- 

 versy arose on the subject ; a prize offered by the Institute of 

 the Netherlands at Amsterdam was awarded to an essay of 

 Schacht's in 1850, which defended Schleiden's theory, and 

 illustrated it by a great number of drawings giving incorrect 

 and indeed inconceivable representations of the decisive points. 

 Von Mohl says very admirably on this occasion (' Botanische 

 Zeitung,' 1863, Beilage, p. 7) : ' Now that we know that 

 Schleiden's doctrine was an illusion, it is instructive, but at the 

 same time sad, to see how ready men were to accept the false 

 for the true ; some renouncing all observation of their own 

 dressed up the phantom in theoretical principles ; others with 

 the microscope in hand, but led astray by their preconceptions, 

 believed that they saw what they could not have seen, and 

 endeavoured to exhibit the correctness of Schleiden's notions 

 as raised above all doubt by the aid of hundreds of figures, 

 which had every thing but truth to recommend them ; and 

 how an academy by rewarding such a work gave fresh, con- 

 firmation to an experience which has been repeatedly made 

 good especially in our own subject during many years past, 

 namely that prize-essays are little adapted to contribute to the 

 solution of a doubtful question in science.' In this case the 

 prize-essay had been refuted before it appeared by von Mohl, 

 Hofmeister and Tulasne. Schacht adhered all the more firmly 

 to Schleiden's theory ; after further controversy, in which other 

 writers of less authority took part, Radlkofer published in 1856 

 a complete review of the question, which fully confirmed Hof- 

 meister's observations, and gave incidentally an account of 

 Schleiden's views in the altered form which they had by that 

 time assumed ; this account showed in fact that Schleiden had 

 completely retracted his former opinions, and in this retracta- 



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