CHAP, in T/ie Morphology of the Floiver 105 



brandt in 1867, as the result of crossing a yellow and a 

 dark-brown race of maize. Not only was the embryo 

 a hybrid, but the endosperm showed characters proper to 

 each of the parents. The phenomenon was observed 

 again in 1872 by Kornecke, and subsequently in 1881 by 

 Focke, who introduced the term xenia for it. Many 

 subsequent observers confirmed these early results. Xenia 

 remained unexplained until Nawaschin's observations were 

 announced, but was then seen to be readily accounted for, 

 indeed, was only what might be expected on the assumption 

 that the fusion of the pollen nucleus with that of the 

 embryo-sac constitutes a sexual union. This view was at 

 once put forward and supported by experimental evidence 

 by De Vries, Correns, and especially by Webber, who carried 

 out a long series of researches at the Nebraska Agricultural 

 Experiment Station in 1898, 1899, and 1900. 



The pursuit of the subject of the pollination of the 

 flower received an additional stimulus from the publication 

 of the Origin of Species, and of Darwin's investigations 

 into the cross and self-fertilization of flowers, which followed 

 after a short interval. Darwin's work extended over the 

 first twenty years of the period under review, and marked 

 by his wonderful patience and careful observation, contri- 

 buted materially to the elucidation of the structure of 

 many of the most complex floral mechanisms. His observa- 

 tions on heterostylism in dimorphic and trimorphic flowers, 

 published in 1869, were especially important. Other 

 workers in the same field were Hildebrand, Delpino, the 

 brothers Fritz and Hermann Miiller, and Axell, all of whom 

 made valuable contributions to this branch of knowledge 

 from 1860 to 1870. Hermann Miiller's presentation of the 

 subject in his great work Die Befruchtung der B lumen in 

 *&73> was one of the most noteworthy features of the 

 study of Natural History of the time, and was for long 

 the standard authority on the subject. 



