1 5 ° 
Double Fertilisation in Angiosperms. 
phenomenon of “ double fertilisation” which is probably of universal 
occurrence in Angiosperms. In Capsella fusion of the polar-nuclei 
was observed to take place at a very late period, yet division of the 
fertilised secondary nucleus was sometimes seen to be well-nigh 
complete while the other antherozoid is still in contact with the 
nucleus of the oosphere. Division of the ovum occurs after formation 
of the first four endosperm-nuclei. In Lepidium there is a slightly 
earlier fusion of the polar-nuclei. 
But Miss Ethel N. Thomas 1 distingushed herself through being 
the first to publish an account of the process of double fertilisation ” 
in Dicotyledons, an undertaking to which she was prompted by Miss 
Ethel Sargant, who had, by her own original observations, confirmed 
the work of Nawaschin and Guignard on the Liliaceae. Miss Thomas 
found that in Caltha palustris the two polar-nuclei were usually 
completely fused before the entrance of the pollen-tube. The 
generative nuclei when emitted are very minute and are either 
oblong, or lens,-dumb bell-, or straight S-shaped. She received the 
impression that the first generative nucleus emitted was the one 
which fertilised the polar-nuclei, for the latter process always 
appeared to be much more advanced than that of the fertilisation of 
the oosphere, and she suggests that this may partly account for the 
fact of the phenomenon being overlooked for so long. The vermi¬ 
form nucleus which fertilises the polar nuclei, increases greatly in 
size, while this is not the case with the other sperm-nucleus. 
The epoch making experiments on the hybrid fertilisation of 
endosperm conducted by De Vries 3 in 1898 afford a most striking 
illustration of the reality, and, in certain cases, the far-reaching 
consequences of the phenomenon of “double fertilisation,” this 
latter, indeed, alone affording an explanation of the facts involved in 
those experiments. De Vries in 1898 possessed forty specimens of 
the variety of the Maize-plant whose grains contain a sugary 
endosperm ; in the following year he obtained from these grains a 
second generation of sixty plants producing sixty-seven spikes full 
of grains all containing sugar only. It is therefore clear that the 
plants destined for his experiments, being the offspring of the same 
original lot, would, if fertilised with their own pollen, have yielded 
pure spikes of sugared grains. The hybrid fertilisation took place 
in August, 1898. At the beginning of the month, before flowering 
1 “On the Presence of Vermiform Nuclei in a Dicotyledon.” — 
“Double Fertilisation in a Dicotyledon —Caltha palustris ” 
(Annals of Botany, Sept. 1902). 
2 “ Sur la fecondatiou liybride de l’endosperine chez le Mais ’’ 
Revue generale de Rot., vol. xii, 1900). 
