1904 | LEWIS: ANOMALOUS DICOTYLEDONS 145 
There are two points of great interest in the study of these 
low plant forms, when they are considered as representing primi- 
tive characters: first, the possibility of determining something 
concerning the origin of the angiosperms; and, second, the ori- 
gin and order of derivation of the monocotyledons and dicoty- 
ledons. 
The gap existing between the seed-bearing plants and the 
pteridophytes of the present time is wide, the nearest approach 
to the seed-habit being. found in the few heterosporous forms. 
It seems probable that the seed-bearing plants had their origin 
from heterosporous pteridophytes of past ages, and that the 
Gymnosperms and Angiosperms arose independently from 
different stocks. On the other hand, from certain similarities it 
seems probable that the monocotyledons and dicotyledons are 
derived from a common stock. If these two divisions had a 
common origin, the question arises as to which is the more prim- 
itive and how the other has been derived from it. There are 
two theories concerning this which are diametrically opposed. 
The theory advanced by Lyon (1901) is that the single 
cotyledon is homologous with the foot of the pteridophytes, and 
that the dicotyledons are derived from the monocotyledons by 
the bifurcation of the single cotyledon as in Nelumbo. How- 
ever true this theory may prove to be, it seems necessary that it 
should be substantiated by a larger collection of facts before it 
can be of great value. If the study of a large number of 
anomalous forms should show the ridge of tissue at the base 
' of the cotyledons of varying height, so that a connected 
could be built, it would in some measure support this t 
although even then the conditions under which the plants develop 
would have to be considered, as the peculiarities might represent 
simply derived conditions. 
Opposed to this theory is that of Miss Sargant (1903) = 
forth in her paper on the origin of the monocotyledons. This 
observer argues that the monocotyledons are derived from the 
dicotyledons, the single cotyledon of the former having arisen 
_ by the union of the two cotyledons of the latter, and that there- 
fore the dicotyledonous plants are the more primitive. This 
series 
heory, 
