Double Fertilisation in Aiigiosperms. . 151 
took place, he cut off the greater part of each male infloresence. 
On emergence of the stigmas from their bracts he powdered them 
at intervals with pollen of a variety of Maize possessing grains with 
starchy endosperm, yet without entirely preventing fertilisation by 
the pollen emanating from the lower branches of their own male 
inflorescences. The result was ten large spikes full of grains. 
Each spike bore two kinds of grains, the greater number being 
starchy like the father, the remainder sugary like the mother. 
These last were largely due to auto-fertilisation, which was proved 
by sowing a portion of them in 1899, when they reproduced the 
sugary variety of the mother. The starchy grains were hybrids , as 
well in their endosperms as in their embryos. The endosperm 
exhibited entirely the character of the father, being well filled with 
starch and containing no visible trace of sugar, being a chalky-white 
within, and having a smooth external surface, without the wrinkles 
so characteristic of the grains of the sugary variety. It was clear 
that these paternal characters had been communicated by the 
second spermatozoid of the pollen-tube. In order to prove the 
hybrid nature of the embryos of these grains he sowed a portion of 
them in 1899 and allowed the plants to be fertilised by their own 
pollen. He obtained a crop of thirty-two plants yielding thirty-five 
spikes, rich in grains All these spikes were of mixed nature, about 
a quarter of the grains were sugary, the three remaining quarters 
being starchy ; the former had reverted to the character of the 
grandmother, the latter exhibited that of the father and grand¬ 
father. The starchy grains of his crossed spikes of 1898 were 
therefore hybrids, capable of reproducing the types of their two 
parents. In all these spikes there occurred no grains of inter¬ 
mediate character, half sugary, and half starchy. 
W. O. Focke, in his great work “ Die Pflanzenmischlinge,” which 
contains a resume of all the experiments conducted by Kornicke, F. 
Hildebrand and De Vries, proposed the term “xeriia” for all 
cases in which an influence of the pollen on the hereditary 
characters of the fruit or grain outside the embryo has been either 
determined or presumed. About the same time as, or a little later 
than De Vries’ work, some detailed investigations and experiments 
were carried out by Correns, 1 as a result of which he established 
several valuable and important corollaries for which we have no 
space here. He at first imagined that xenia was due to a fusion of 
half the generative nucleus (as a result of division of the latter) with 
1 “ Untersuchuiigen Tiber die Xenien bei Zea Mais ” (Bericbte 
der deutscli. bot. Gesellschaft, 1S99), etc. 
