178 ANGIOSPERMS. 
fusion in species of Z//um (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 
Fic. 75.—Fusion of second male nucleus with polar nuclei in Lzdizs om srtagon. 
A, an S-shaped male nucleus applied to the upper polar nucleus. 
8B, 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 Zzlzum 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 7ilfa celliana and 7. sylves- 
trzs regards the process as a pseudo-fecundation. . 
From a series of important experiments on the hybridization of 
several varieties of Zea mays, Webber (1900) 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, 
