22 THE AMERICAN NATURALIST. (VoL. XXXIX. 
ledons of the angiosperms are morphologically of one category. 
In 1809 Poiteau published the theory that the epiblast of cer- 
tain grasses represents a vestigial cotyledon thus indicating a 
dicotyledonous origin for these plants. This hypothesis has won 
many adherents and but recently Van Tieghem ('98) has, on the 
strength of it, placed the Grasses with the Nymphzeaceze under 
a third class of angiosperms which he calls Liorhiza dicotyledons. 
Van Tieghem's classification has been adequately dealt with by 
Balfour (:01, :02) and needs no further attention from us at' 
this time. Poiteau’s idea of the reduction of one cotyledon was 
employed by Henslow (93) to explain the origin of the mono- 
cotylous condition throughout the Monocotyledons. 
Agardh (29-32) also accepted Poiteau's interpretation of the 
grass-embryo but considered the Graminex the only true mono- 
cotyledons. The’ Naiadex, Palmz, Aroidez, Lilieze and Scita- 
minez, and probably other families of monocotyledons, he 
classed as syncotyledones, considering the terminal structure of 
their embryos to represent two cotyledons which had become 
fused into a single member. 
In a previous paper, the writer (:02) also concluded that the 
cotyledon of a monocotyledon was equivalent to both of the coty- 
ledons of a dicotyledon, but that the monocotylous condition 
was the more primitive and that from this the dicotylous condi- 
tion had arisen through a bifurcation of the originally single 
cotyledon. The morphological value ascribed to the cotyledon 
led primarily to this conclusion which was further strengthened 
by embryological studies in the Nymphzacez. 
i S a series of admirable papers, Miss Sargant (: 02, :03, :04) 
as brought together much evidence, of which her own research 
work has furnished a very important part, showing that the 
cotyledon of a monocotylous embryo is equivalent to both of the 
Bes of the dicotylous embryo. Add to this the evidence 
fom the Ny niphacee embodied in the recent works of Lyon 
Schaffner (: 04), and York (104) and the con- 
i In considering the phylogeny 
view suggested by Aga] ae e BREUER er 
bien deed: y poo that the monocotylous condition has 
rıved trom the dicotylous condition through the fusion of 
am 


