1914] MANEVAL—MAGNOLIACEAE 13 
Thus far the monocotyledons have been left out of account 
in looking for primitive angiosperms. Let us now turn to this 
‘group. 
The remarkable uniformity in the development and mature 
condition of the male and female gametophytes of monocotyledons 
and dicotyledons has been brought forth repeatedly as the strongest 
argument in favor of a monophyletic theory. In spite of objections 
such as the claim that ‘‘similarity in structure may be the out- 
growth of the changes that resulted in the evolution of seeds” 
(6), it seems that we are far from the point of even thinking of 
abandoning this as well-nigh irrefutable evidence of close genetic 
relationship between the two great classes of angiosperms. 
Within the last few years the striking similarity in the seedling 
structure of dicotyledons and monocotyledons has been demon- 
strated in many forms. Although the generalization that ‘‘onto- 
geny repeats phylogeny”’ has likely been overworked, yet if there 
is anything at all in this rule, then the evidence from seedling 
structure deserves its full share of consideration. 
In favor of the view that the two groups have originated in- 
dependently are the differences in their anatomy, and in the 
development and mature condition of the embryo. As a result of 
recent study, however, we learn that anatomically the structure 
of seedlings in particular, but also of mature individuals in the 
two groups, offers many striking points of resemblance. Other 
differences, generally regarded as secondary in importance, are 
seen in the venation of the leaves, in the grandifoliate as opposed 
to the parvifoliate habit, and in floral symmetry. 
The principal resemblances and differences between monocotyle- 
dons and dicotyledons on which present phyletic theories are based 
have been mentioned. In reviewing these theories we may recall 
the fact that while according to most if not all monophyletic theories 
proposed until recently, dicotyledons were assumed to be derived 
from monocotyledons, students of phylogeny today quite generally 
hold the opposite view. WoRrSDELL (33), however, is still inclined 
to the view that monocotyledons rather than dicotyledons are 
primitive. He believes that ‘‘angiosperms have developed directly 
from an ancestor belonging to the bryophytic level, and that they 
