i 7 S 



ANGIOSPERMS. 



fusion in species of Lilium (Fig. 75, A, B, C). An account of the 

 fusion of one of the male nuclei with the polar nuclei was first pub- 

 lished by Nawaschin ('99) and made known to botanists in general 

 by a reference in the Botanisches Centralblatt. 



Guignard ('99) in the same year published the results of his obser- 

 vations confirming the statement of Nawaschin. He figured the second 

 vermiform male nucleus in contact with one or both polar nuclei, but 

 none of Guignard's figures showed an actual fusion. Although we 

 are justified in assuming that sexual nuclei, when brought in contact, 

 will fuse, yet the possibility is not excluded that since the sexual nuclei 

 remain side by side for some time before fusion takes place, the causes 

 which have been long known to operate in preventing the formation 



FIG. 75. Fusion of second male nucleus with polar nuclei in Lilium -nurtagon. 



A, an S-shaped male nucleus applied to the upper polar nucleus. 



B, second male nucleus (shown only in part) and the two polar nuclei close together. 



C, all three nuclei fusing. 



of seeds in certain species of Lilium may also prevent the complete 

 fusion of these nuclei after having come in contact. 



The fusion of a male nucleus with the endosperm nucleus has received 

 different interpretations at the hands of the several investigators. Na- 

 waschin (1900), H. De Vries ('99, 1900) and Correns ('99) evidently 

 see in this fusion a true sexual process, basing their conclusion largely 

 upon the hybrid character of the endosperm of certain varieties of Zea 

 mays. Guignard in his paper upon Tulifia celliana and T. sylves- 

 tris regards the process as a pseudo-fecundation. 



From a series of important experiments on the hybridization of 

 several varieties of Zea mays, Webber (1906) arrives independently at 

 the same conclusion as De Vries, namely, that certain phenomena of 

 xenia are the result of the fusion of one of the male nuclei with the 

 endosperm nucleus. As a result of the crossing, the endosperm, pro- 

 duced in the same embryo-sac with the hybrid embryo sporophyte, 



