68 Sargant. — Theory of the Origin of Monocotyledons 
i. Comparative Antiquity of Monocotyledons 
and Dicotyledons. 
The Angiosperms form a very well-defined group, and 
modern research has tended to show that the gulf between 
them and the Gymnosperms is even wider than was formerly 
supposed. To borrow an expressive phrase, we have begun 
to realize the isolation of the Angiosperms. 
Within this group the Monocotyledons are divided from 
the Dicotyledons by a number of natural characters, but 
these two classes are undoubtedly far more closely related 
to each other than is either of them to any other group of 
plants. The presumption is strong that they come from 
a common stock. 
A generation ago the Monocotyledons were regarded as 
probably the older group, but botanists have never been 
unanimous in this opinion, and of late the evidence of fossil 
botany has on the whole inclined the scale in the opposite 
direction. The case is so admirably summed up by Professor 
Bayley Balfour (in the article on Angiosperms, Supplement 
to Encyclopedia Britannica, vol. xxv, 1902), that I am tempted 
to quote his judgement in full : — 
‘ The position of Angiosperms as the highest plant-group 
is unassailable. . . . We readily recognize in them now-a- 
days the natural classes of Dicotyledones and Monocotyle- 
dones, distinguished alike in vegetative and in reproductive 
construction, yet showing remarkable parallel sequences in 
development ; and we see that the Dicotyledones are the 
more advanced and show the greater capacity for further 
progressive evolution. But there is no sound basis for the 
assumption that the Dicotyledones are derived from Mono- 
cotyledones ; indeed the palaeontological evidence seems to 
point to the Dicotyledones being the older. This however 
does not entitle us to assume the origin of Monocotyledones 
from Dicotyledones, although there is manifestly a temptation 
to connect helobic forms of the former with ranal ones of the 
