150 
WALTER P. THOMPSON 
Not only does it satisfy all the conditions in Gnetum but it also 
harmonizes these conditions with those in both the other genera of 
Gnetales. 
The conclusions which have just been reached have a profound 
significance in connection with the relationship between Angiosperms 
and Gnetales. If the reduction hypothesis is correct the ancestral 
flower of the Gnetales had all the parts of the Angiosperm type ar- 
ranged in the same manner as that type. We may now enquire 
whether those individual parts correspond exactly. 
It is clear that what we have called an ovary in Gnetum is in all 
essential respects the same as that of Angiosperms. It is a sac de- 
rived from foliar members enclosing an ovule and bearing a special 
structure on which the pollen is received and in which some of it 
germinates. The real question appears to be whether Gnetum is a 
true Angiosperm. For all practical purposes it is Angiospermous. 
The ovule is single and orthotropous, rising from the base of the 
ovarian cavity. These are the conditions in some of those Angio- 
sperms which are classified on the basis of other characters at the 
bottom of the phylum — the Amentales. Some of the latter, e. g., 
Salicaceae, have more than one ovule in each ovary but even in Gnetum 
I have seen in abnormal instances two ovules developing in an ovary. 
The chief difference as far as the ovule is concerned is the absence 
of integuments in Gnetum (according to our interpretation). But 
the ovules of certain Angiosperms also lack integuments and it is 
not strange that the integuments should disappear in flowers reduced 
in so many other ways as are those of Gnetum. 
In most Angiosperms the ovules are attached to the side of the 
sporangial cavity and are therefore said to be foliar. Those which 
rise from the bottom of the cavity are obviously attached to an axis 
and are said to be cauline. The old view that ovules are modifications 
of some part of a leaf implied that the foliar condition is primitive 
and that the cauline one has been derived from it. This conclusion 
is opposed by the evidence derived from the distribution of the two 
types, the cauline condition being found chiefly among primitive 
forms and the foliar among the higher families. The mistake lies 
in the original assumption that ovules are modifications of some part 
of a leaf. Ovules are ancient members of the plant body and hold no 
necessary relation to either leaf or stem. As stated by Coulter and 
Chamberlain (8) they have a history which probably antedates that of 
