49 ° Arber and Parkin. — Studies on the 
obtained from other sources, will itself shed light on the relationships of the 
former.’ 1 
To this conclusion we still adhere, so far as the morphology of the 
fructifications of the Gnetales is concerned. But we propose to consider 
here whether the Strobilus Theory of Angiospermous descent, as outlined 
in our previous paper, will not help towards a clearer insight into the real 
relationships existing between the two groups, and thus permit us to find 
a place for the Gnetales in the table of phylogenetic relationships which 
is given at the conclusion of that paper. It will be found that we, after 
much consideration, have arrived by this means at an hypothesis which 
appears to us to remove, for the time being at any rate, the great uncertainty 
which has hitherto existed in regard to the closeness of these relationships. 
It has been a vexed question for many years past whether the Gnetales 
themselves did not give rise to the Angiosperms. Previous conclusions on 
this point will be fully reviewed in the next section of this paper. We may, 
however, illustrate here the diversity of opinion which has existed by means 
of two quotations, between which a period of sixteen years elapsed. On 
the one hand, in 1885, the French Palaeobotanist, Renault, 2 who had paid 
considerable attention to certain Palaeozoic fructifications ( Gnetopsis ) then 
believed to belong to the Gnetales, decided that ‘ Les Gnetacees etablissent 
une transition entre les Gymnospermes et les Angiospermes ’. On the other 
hand, in Coulter and Chamberlains 3 authoritative summary of the Gymno- 
sperms, published in 1901, we find the following statement with regard to 
the Gnetales : ‘ Certain angiospermous characters which they display have 
suggested that they may have given rise to Angiosperms, but such a theory 
seems to have been abandoned by most morphologists.’ 
We are well aware that the problem presents great difficulties. There 
are but three genera in existence, two of which are very highly specialized 
in relation to their environment, and the fructifications of all three show 
comparatively little variety. Consequently few clues are afforded respecting 
the possible homologies of their individual organs. When, in addition, it is 
admitted that the fossil record of the group is really nil, it is obvious 
that the data at our disposal are of the slightest. It will therefore be to 
the credit of what we have elsewhere termed the Strobilus Theory, 4 if, 
by its aid, we can evolve a reasonable hypothesis of the relationships of 
the Angiosperms to the Gnetales. It may also be remarked that the two 
theories, the Strobilus Theory of Angiospermous descent, and the parallel 
and similar theory about to be elaborated here respecting the Gnetales, 
stand or fall together. 
Although, so far as we can determine, there is at present no evidence 
of the Gnetales in the fossil state, we are not thereby precluded from an 
1 Arber and Parkin (’07), p. 34 . 2 Renault (’85), vol. iv, p. 1 7 r * 
3 Coulter and Chamberlain (’01), p. 112 . 4 Arber and Parkin (’07), p. 36 . 
