of Fertilization in Angiosperms. 691 
of motion within the embryo-sac, and if so, can they be con¬ 
sidered as much reduced spermatozoids ? 
3. What light is thrown by these researches on the homology 
of the structures contained in the typical embryo-sac of 
Angiosperms ? 
4. Can the fusion of the second generative nucleus with 
the definitive nucleus of the embryo-sac be considered as 
a true act of fertilization? 
It will be convenient to deal with these questions separately, 
and to consider the work of the past two years with reference 
to each in turn, rather than to adopt a strictly chrono¬ 
logical arrangement. I shall also mention in connexion with 
each any work of an earlier date which seems to me to bear 
on the point, or to suggest an opening for further research. 
I. Occurrence of Double Fertilization 
in Angiosperms. 
Considering that we are dealing with the work published 
during little more than a year, and that the labour involved 
in such research is great, the number of species in which 
double fertilization has been observed since the original dis¬ 
covery may be called large. The following is a list, as 
complete as I can make it, up to the present date (Nov. 14, 
1900). It includes the original observations on Lilium. For 
convenience of reference the specific name used by the 
observer is retained. 
Order. 
Species. 
Observer. 
Liliaceae 
Monocotyledones. 
Lilium Mart agon. 
Nawaschin. 
L. pyrenaicum. 
Guignard. 
Guignard. 
Fritillaria tenella. 
Nawaschin. 
F. Meleagris. 
Guignard. 
Tulepa Gesneriana. 
Guignard. 
T. Celsiana. 
Guignard. 
T. sylvestHs. 
Guignard. 
Endymion nutans. 
Guignard. 
