No. 457.] EMBRYO OF THE ANGIOSPERMS. I5 
cotyledons, and merged gradually into recognizable Dicotyledons. 
The emerging of Dicotyledons from this vague group either 
indicates that Monocotyledons and Dicotyledons originated inde- 
pendently or that the Proangiosperms were transition forms 
between Monocotyledons and Dicotyledons. This latter alter- 
native is in turn inconceivable, especially since the most primi- 
tive Dicotyledons are recognized to be even more primitive than 
any of the Monocotyledons.....In our judgment the evidence 
is strongly in favor of the independent origin of the two groups, 
which have attained practically the same advancement in‘the 
essential morphological structures, but are very diverse in their 
more superficial features. Their great distinctness now indi- 
cates either that they were always distinct or that they originated 
from forms that were really Proangiosperms and neither Mono- 
cotyledons nor Dicotyledons.” 
Few morphologists will agree with the statement that the only 
morphological argument in favor of the monophyletic theory is 
to be derived from the similarity in embryo and endosperm 
development. There is in both classes a remarkable conformity 
to one common plan in all phases of their organogeny ; not only 
in the embryo-sac, but in the development of floral structures, 
androecia, gynoecia, ovules, seeds and fruits. While many simi- 
larities in plant structures have undoubtedly resulted through 
parallel development, is it not carrying the idea to an unwar- 
ranted extreme when it is attempted to explain all the exact 
details of development, which obtain alike in both classes of 
Angiosperms, as simply parallelisms, especially since no tangible 
evidence is brought forward to justify it ? 
If the fundamental differences in embryogeny are to be 
delineated by the exceptionally perfected embryos of Alisma and 
Bursa, as is so generally stated, they might be considered hard 
to reconcile. If on the other hand they are to be determined 
by a comprehensive comparison of the various types of embryos. 
to be found in the two classes, the real difficulty is not, how to 
reconcile these differences, but how to locate them. An exam- 
ination of recent embryological work ! will show that no funda- 
1Sterckx ('99), Lyon (:01), Cook (: 02), Schmid (: 02), Sargant (:02, : 03, : 04), 
Schaffner (:04), York (:04). 
