Enstehung 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 controversy 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 confirmation 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 Hofmeister'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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Chap. i.]
Investigation of the fertilization-process.
435
