Evolution of the Angiosperms. 
495 
More modern researches, however, have tended to widen greatly the gap 
between the Gnetaceae and the Angiosperms. Bower , 1 from his examina- 
tions of the germination and seedling structure of W elwitschia and Gnetuni 
Gnemon , concluded that the Gnetaceae are a more natural group than has 
hitherto been supposed, and that Gnetum is, in reality, scarcely more 
closely comparable with the Angiosperms than the other two genera. 
Lotsy , 2 from his researches on Gnetum , came to the conclusion that in 
all probability no Angiosperm had a Gnetacean ancestor, but that the 
Gnetaceae arose quite independently. He would derive them directly 
from heterosporous Pteridophytes, as a separate line quite distinct from 
those giving rise to the Gymnosperms and Angiosperms. Lignier , 3 in 
a theoretical paper on the relationship of the fructifications of the Gymno- 
sperms to the Angiosperms, finds that the Gnetaceae cannot have been 
intermediate between these two large groups. 
Land , 4 in his recent paper on Ephedra trifurca , remarks that ‘ there 
is no proof that the Gnetales have been derived from or are directly related 
to any living group’. If they are ‘related to the Coniferales at all, it 
must be to the Taxaceae’. He thinks the Gnetales are better regarded 
as a modern group. 
At the present time, however, some botanists are not content to 
abandon all hope of connecting the Gnetaceae and the Angiosperms. 
The points of resemblance are too many and too striking for homoplasy 
to afford a sufficient explanation. Some quite recent attempts 5 to link 
these two groups may now be briefly considered. 
Since the publication of our previous paper, Professor Wettstein 6 has 
elaborated for the first time the theory on which depends the belief that 
the hermaphrodite flowers of the Angiosperms, with a conspicuous perianth, 
are derived from unisexual, apetalous forms. He traces the origin of the 
Polypetalae from the Gymnosperms, making use of Ephedra and Casuarina , 
as connecting links. Porsch 7 also finds support for this view by an appeal 
to embryological evidence. 
Hallier 8 at one time attempted to revive the supposed relationship 
between the Gnetales and the Loranthaceae, a view which we gather he 
has recently abandoned. 
We may thus conclude from this historical sketch that the balance 
of opinion at the present time appears to be against the views, either 
that the Angiosperms have sprung from the Gnetales, or that the Gnetales 
hold an intermediate position between Gymnosperms and Angiosperms. 
1 Bower (’82), p. 298. 2 Lotsy (’99), p. 100. 
3 Lignier (’03). 4 Land (’07), p. 288. 
5 A short paper by Miss Benson (’04) on this subject was referred to on p. 33 of our previous 
paper (’07). The author informs us that we have misunderstood her argument, which we much regret. 
6 Wettstein (’07 1 ), vol. ii, part ii, first half, p. 203, and (’07 2 ). 
7 Porsch (’07), pp. 14-15. 8 Hallier (’07), p. 497. 
