699 
of Fertilization in Angiosperms. 
produces the male elements. This last view is implied in 
Le Monnier’s explanation of the fusion of the polar nuclei 
as a sexual act (see Groom, 22 , p. 133). The upper polar 
nucleus must, as the sister of the egg-nucleus, represent the 
female element in the conjugation. The lower polar nucleus 
must therefore represent the male element. But this assump¬ 
tion is no longer necessary, as we now know that there is a 
triple fusion, in which the second generative nucleus supplies 
the male element. Thus the third suggestion (c) has been 
shelved, and we are left with two. 
There is nothing in the discovery of double fertilization to 
decide between the two views which remain. Future research 
may reveal a chain of forms linking the whole structure of 
the embryo-sac before fertilization with some more primitive 
type in which the homologies with lower plants are clear. 
Many species are known in which the antipodals increase in 
number. For references to the literature of the subject I 
must refer to Strasburger’s paper ( 11 , p. 311). As suggested 
above, there is no reason to suppose that all these forms are 
adaptive because some are so. 
The discovery of double fertilization has, however, a direct 
bearing on the vexed question of the origin of the Angiosper- 
mous endosperm. This tissue was considered by Hofmeister 
to represent a prothallus, the development of which was 
arrested before fertilization. The fusion of the two polar 
nuclei which takes place about the same time as the fertiliza¬ 
tion of the egg-cell gave the signal for renewed development. 
This view held its ground for a generation, and gave rise to 
the accepted nomenclature. The food-tissue formed by 
Gymnosperms within the embryo-sac before fertilization, which 
undoubtedly represents the female prothallus, is generally 
called the endosperm to mark its supposed homology with 
the tissue we are now considering in Angiosperms. Stras- 
burger (11)—himself a supporter of the classical view—has 
justly remarked (p. 314) that the true issues would be rendered 
clearer if we called the Gymnospermous tissue a prothallus, 
and confined the term endosperm to Angiosperms. This is a 
