Evolution of Monocotyledons. 289 
groups being the most nearly related. 1 There is no evidence that 
either group was derived from the other, but there are, according to 
Bessey, structural indications that Monocotyledons must rank lower 
than Dicotyledons. He believes that the earliest forms of both 
groups made their appearance almost simultaneously in late Permo- 
Carboniferous or early Mesozoic times, but palaeobotanical investi¬ 
gations show that there is no actual reliable evidence for the 
presence of Angiosperms before the Cretaceous, 2 though both sub¬ 
groups appear to be well-established by the end of that period, 
according to the work of Drs. Stopes and Fujii (67, 68). A recent 
paper by Horwood (36) gives a useful summary of fossil Mono¬ 
cotyledons, showing that the first authentic specimens are from the 
Cretaceous. Horwood agrees with Bessey in believing that Mono¬ 
cotyledons and Dicotyledons arose from a common ancestor, 
resembling an Alismaceous or Liliaceous type on the one hand and 
a Ranalean type on the other. 
Engler (21) deals with the Monocotyledons before the Dicoty¬ 
ledons, explaining that he leaves them in the position they have 
generally held in previous classifications, because he does not 
consider that there is sufficient evidence for the growing idea of 
their derivation from Dicotyledons. He prefers to regard them as 
two groups of equal value (21, p. vi of preface). Of the phylogeny 
of the Angiosperms as a whole, he gives very little idea, but considers 
both Monocotyledons and Dicotyledons as being polyphyletic (20, 
pp. 371-380). 
Warming (74) also places the Monocotyledons first in his 
system, and follows Engler in preferring, in the present state of our 
knowledge, to consider Monocotyledons and Dicotyledons as two 
independent lines of evolution. 
It may be remarked before passing on to other systems that 
this view of independence of the two groups was suggested as early 
as 1875 by Kny (37, p. 61). It was held by Drude (17, pp. 184, 304) 
and has had various supporters who have set forth their ideas of 
phylogeny more or less definitely. For example, Coulter and 
Chamberlain (12, pp. 284, 285) derive the Monocotyledons from an 
Isoetes -like ancestor, and the Dicotyledons from a Selaginella -like 
type on the grounds of similarity of the embryos. As an alternative 
they suggest that both came from extinct lines of Eusporangiate 
' Cf. Fritsch (23). This author believes that the Ranales and Helobieae 
had a common origin in extinct and unknown forms. 
2 Cf. Scott (64, p. 660); Seward (65, p. 220); Coulter and Chamberlain 
(12, p. 273). 
