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Primitive A ngiosperms. 
The present paper is an abstract of those lectures. It may be con- 
sidered as a complement to that part of Messrs. Arber and Parkin’s memoir 
which deals with the immediate predecessors of our living Angiosperms. 
The evidence brought together in that memoir relates mainly, though not 
exclusively, to floral structure. I am in complete agreement with the 
general conclusions reached by its authors. Accordingly, I have attempted 
no separate reconstruction of the flower of the Primitive Angiosperms. 
The evidence considered in the present paper, then, is in the main 
derived from the study of living Angiosperms. This evidence will be used 
to reconstruct a comparatively recent race of plants — the latest ancestors 
which Monocotyledons and Dicotyledons had in common. In dealing with 
their floral structure Messrs. Arber and Parkin’s results will be accepted as 
a working hypothesis. 
Before discussing the evidence on which we may hope to reconstruct 
the Primitive Angiosperms, it is essential to inquire whether such a race 
ever existed. Do all our living Angiosperms spring from a common stock ? 
If not — if they have been derived from different descendants of the original 
Pteridosperm, at several epochs and through distinct lines of descent — the 
problem becomes very much more complicated. Indeed, in the present 
state of our knowledge it could not be profitably attacked. 
The argument in favour of the monophyletic origin of Angiosperms 
may be briefly summarized thus : The characters which Monocotyledons 
and Dicotyledons have in common are too numerous and too uniform 
to have been acquired independently in response to similar conditions. 
They must be derived by inheritance from a common stock — a race of 
Angiosperms, since it possessed the characters common to both classes 
within that group. 
This argument appears to me conclusive, but, while the probability 
of such origin is called in question by botanists of authority, 1 the truth of it 
cannot be assumed without discussion. The present essay is, therefore, 
divided and subdivided as follows : — 
I. Reasons for believing that Angiosperms are monophyletic. 
II. Reconstruction of the primitive race of Angiosperms. 
1. Floral structure. 
2. Stem anatomy. 
3. Number of cotyledons. 
4. Minor characters considered in connexion with phylogenetic 
schemes. 
Monophyletic Origin of Angiosperms. 
The remarkable isolation of Angiosperms in the vegetable kingdom is 
due of course to the absence of intermediate forms either living or fossil. 
1 Balfour (8) ; Coulter (18) ; Coulter and Chamberlain (19), p. 283. 
K 2 
