16 THE AMERICAN NATURALIST. (Vor. XXXIX, 
mental differences can be distinguished. Coulter and Chamber- 
lain themselves in a previous chapter of the same work, write, 
“ The distinction between Monocotyledons and Dicotyledons is 
not always clear in the embryo." 
Should fundamental differences in the structure of the stem 
and its vascular bundles be pointed out, this “ rebutting propost- 
tion” might prove a serious one. It is certain, however, that 
such an opinion can carry little weight when opposed to the 
conclusions of careful investigators supported by their researches. 
And almost without an exception, students! who have actually 
worked on the stem anatomy of the angiosperms with a view to 
determining their phylogeny, concur in the opinion that here 
also the evidence is for and not against a monophyletic origin. 
There is a characteristic type of stem and bundle structure 
prevalent in each class it is true, but in certain plants of both 
they so closely approximate a common type that no hard and 
fast line can be drawn between the classes on this basis. That 
both types have been evolved within the angiosperms from one 
fundamental pattern is amply demonstrated by existing plants as 
the above mentioned students have shown. Coulter and Cham- 
berlain (:03) would place the Nymphsacex among the dicoty- 
ledons because of their embryo-characters ; but no one has 
ever been able to show that the stem structure of the Nymphe- 
aceze is other than essentially that characteristic of monocotyle- 
dons. In placing the Nymphzacez as they do, they themselves 
admit that there are no differences in stem structure between 
the plants of the two classes which are fundamental. 
As to the historical testimony which is to be derived from 
palzeobotany, Seward (: 03) has shown that, in the extent of our 
present knowledge, it is to be considered of questionable value. 
While giving due consideration to these adverse opinions ; 
admitting that an independent origin of the monocotyledons and 
dicotyledons is not inconceivable, and that all their common 
morphological, structural and cytological peculiarities might be 
simply parallelisms ; still we are justified in accepting the 
strongly fortified conclusion, borne out by all obtainable evi- 
* Queva ('99), Jeffrey (: 00, :03), Worsdell (: 02), Sargant (: 03). 


