528 Thomas.—Double Fertilization in a 
travels to the middle of the sac, and there coalesces with the 
upper polar nucleus, and then both fuse with the lower polar 
nucleus. Guignard agrees with this, and furthermore states 
that the polar nuclei may have approached 1 one another 
before the generative nucleus joins them, and gives many 
figures showing the triple fusion. He gives instances also in 
which, when the polar nuclei are still separate, the generative 
nucleus joins the lower one. However this may be, the 
definitive nucleus which later gives rise to the endosperm 
is the product of the fusion of three nuclei of very different 
origin. The upper polar nucleus is sister-nucleus to that of 
the oosphere, and were it not for the presence of the lower 
polar nucleus, which is vegetative in character, the fusion of 
the second generative nucleus with the upper polar nucleus 
would be a true fertilization precisely equivalent to the 
fertilization of the oosphere by the male nucleus. 
In addition to this most important discovery,-both observers 
found that the generative nuclei had a very remarkable shape. 
They are long and narrow, and twisted in every conceivable 
manner, so that the term vermiform has been applied to them, 
and their appearance suggestedto Guignard their strict analogy 
to antherozoids. The contortions are particularly noticeable 
in the second generative nucleus on its journey to the polar 
nuclei, and no doubt indicate the wriggling movement by which 
it travels through the sac. 
When these accounts were published, Miss Sargant found 
that she had preparations of Lilium Mar tag on made years 
before which showed the vermiform nuclei and double fertiliza¬ 
tion extremely well 2 , and as she still possessed the material 
which furnished these slides, she proposed that I should cut 
some of it to see how readily this stage could be obtained. 
As it was not convenient in some ways to work at Reigate, 
Professor Farmer very kindly consented to my working at the 
Royal College of Science, South Kensington, and throughout 
has given me the greatest assistance. I went there in May of 
1 Comptes rendus, p. 4 of separate copy. 
2 Sargant, Proc. Roy. Soc., May. 1899. 
