506 Arber and Parkin.— Studies on the 
the development of its embryo it obviously follows the type of the 
Coniferae, and indeed approaches them in some respects more nearly than 
either Ephedra or Wehvitschia \ 
We are inclined to think that too much weight has been attached to 
these embryological dissimilarities from the point of view of the relationship 
of the three genera to one another. The great contrast between the em- 
bryo-sacs of Gnetum and Welwitschia on the one hand, and Ephedra on the 
other, is no doubt remarkable, and, apart from other morphological considera- 
tions, it might be perfectly legitimate to conclude that their relationships 
were distant. But it is unwise to reason phylogenetically from the evi- 
dence of one organ, to the neglect of others, even though that organ be the 
female gametophyte. We think the sum total of the agreements between 
the three genera is too strong to permit of the complete separation of 
Ephedra from Gnetum and Welwitschia. 
We would suggest that the immediate ancestors of the Gnetales had 
a fairly typical Gymnospermous embryo-sac, which has more or less 
persisted in the case of Ephedra , but which in Gnetum and Welwitschia 
has undergone considerable reduction with peculiar modifications. 
We now turn to the question of Angiospermous affinities. The 
suppression of the archegonia, the formation of a storage tissue after 
fertilization, and the discovery of nuclear fusions quite recently made 
by Berridge and Sanday, are all facts which have been regarded as 
rendering hopeful the possibility of interpreting the Angiospermous embryo- 
sac by means of the Gnetales. Though not wishing to seem to depreciate 
in the least the great value of these embryological observations, we are 
doubtful if this hope will be realized. 
Miss Sargant , 1 in her paper in the April number of the Annals, has 
discussed the Gnetalean embryo-sac, and has pointed out that no tissue 
‘ in Gnetum , nor, so far as we know, in Wehvitschia, can be considered 
as the direct representative of the Angiospermous endosperm ’. In other 
respects also the resemblances appear to us to be more superficial than 
real. While no doubt in the history of the evolution of the embryo-sac of 
both Gnetum and Wehvitschia , and also in the Angiosperms, a correspond- 
ing stage was at one time reached when the archegonia became sup- 
pressed, yet since then further modifications have taken place along different 
lines. In the case of the Angiosperms the chief modern speciality has 
been the formation of endosperm as a result of double fertilization, while 
in the Gnetalean genera special features, such as the prothallial tubes, have 
been evolved. 
The outstanding characteristics of the embryo-sacs of Wehvitschia and 
Gnetum as compared with Ephedra may in some measure be analogous 
to those of Peperomia 2 as compared with Piper , and are thus more of 
1 Sargant (’08), p. 135 . 2 Johnson (’05) and (’07). 
