Double Fertilisation in Angiosperms. 
i52 
the secondary nucleus of the sac. The process he regards as a case of 
of true fertilisation inasmuch as the Maize-grain, produced as a 
result of pollination by another race, contains, besides the bastard 
embryo, a bastard-endosperm. A second possible explanation offered 
by him is that the bastard-embryo exercises an enzymatic action on the 
endosperm, this being not so unlikely, seeing that it is merely a 
question of formation of colouring-matter or of closely-allied reserve- 
stuffs It is to be noted that xenia-formation has been observed by 
Giltay in the Rye, where it corresponds to one of the special cases 
in the Maize. Correns points out that cases in which races or 
closely-allied species exhibit essential differences in the character of 
the endosperm, are, unfortunately, of rare occurrence. 
The publication of Nawaschin and Guignard’s observations 
solved the whole problem of xenia or hybrid endosperm-formation, 
for it is manifest that a fusion of the second male or sperm-nucleus 
emanating from the pollen of the foreign race with the definitive or 
secondary nucleus of the embryo-sac, the division of which latter, 
as we know, invariably gives rise to the endosperm, would supply all 
the necessary conditions under which a hybrid endosperm could be 
produced; for just as the fertilised ovum gives rise on division to an 
embryo combining in itself the characters of the two parents from 
which the first generative nucleus and that of the oosphere 
respectively proceeded, precisely the same will be true of the 
product of division of the definitive nucleus “ fertilised ” by the 
second generative nucleus of the pollen tube. 1 
We have reserved until last the observations or theoretical 
considerations of the two authors who appear, in our opinion, to 
shed the brightest light upon this most interesting problem of 
“double fertilisation.” To our thinking Strasburger 2 in this matter 
maintains his great reputation as a leader in all that concerns 
investigation into the wonderful developmental history of the 
embryo-sac. He himself observed “ double fertilisation ” in several 
Orchids and in Monotvopa Hypopitys. He regards the passage 
through the embryo-sac of the second sperm-nucleus (which, in the 
plants examined by him, did not always exhibit a worm-like shape) 
as probably of a passive nature. His explanation of the whole 
course of events in the embryo-sac is as follows:—The prothallus- 
formation in the embryo-sac of all Angiosperms is divided into two 
1 For an account of Correns’ work and ils relation to Mendel's 
laws of hybridism, see The New Phytoi.ogist, vol. I., 
1902, p. 103., et scq. 
2 “ Einige Bemerkungen zur Frage nacli der ‘ doppelten 
Befruclitung’ bei den Angiospermen ” (Botanisclie Zeitung, 
1900). 
