THE ORIGIN OF MONOCOTYLEDONY 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 187 
Joun M. CovuLTER AND W. J. G. LAND © 
(WITH PLATES XXVIII AND XXIX AND TWO FIGURES) 
The origin of Monocotyledons from the Archichlamydeae seems 
well enough established to need no discussion in this connection. 
he evidence of vascular anatomy, supported by the historical 
record, as well as by general morphological considerations, seems 
to be explicit. It remained to obtain evidence of the transition 
from dicotyledony to monocotyledony.. This seemed to be a 
peculiarly difficult situation, for it appeared to involve much more 
than the number of cotyledons. The difference in number was dis- 
posed of in two ways, the monocotyledonous condition being said 
to have arisen either by a fusion of the two cotyledons or by a 
suppression of one of them. Each of these views can be supported 
by a considerable body of evidence, hased upon vascular anatomy 
and upon many intermediate stages in fusion or in elimination. 
The real difficulty in the situation, however, appeared to be in the 
fact that in Monocotyledons the cotyledon is a terminal structure, 
and in Dicotyledons the cotyledons are lateral structures. How 
could the terminal cell of a filamentous proembryo which had been 
producing a stem tip change its function and persistently produce 
a cotyledon? Any comparison of the proembryos of Capsella and 
Alisma, the two accepted types of Dicotyledons and Monocoty- 
ledons, emphasizes this difficulty. 
A clue to this problem was furnished by the seedlings of Cyr- 
tanthus, a South African genus of Amaryllidaceae, which was 
investigated by Miss FARRELL,’ a graduate student of this depart- 
ment. In accordance with this suggestion, seeds of numerous 
Monocotyledons were obtained from South Africa and Australia, 
These were germinated and an abundance of material obtained for 
study. 
, Marcaret E., Ovary and embryo of Cyrianthus sanguineus. Bor. 
Gaz. $7:428-436. pl. 24. figs. 3. 1914. 
509] [Botanical Gazette, vol. 57 
