1904] SARGANT: EVOLUTION OF MONOCOTYLEDONS 333 
more primitive forms these bundles are massive and very widely 
separated.*3 The suggestion that each represented the midrib 
of an ancestral cotyledon seemed an adequate and simple expla- 
nation of the phenomenon, and it was much strengthened when 
I examined a number of dicotyledons—all from the Ranales— 
in which the cotyledons are partially united. The simplification 
of structure caused by this incomplete union was found to reduce 
the vascular symmetry of the ranal seedling (Eranthis, Podophyl- 
lum) to a skeleton much resembling that previously described as 
primitive among monocotyledons (Anemarrhena, Albuca). 
An angiospermous plant possessing two seéd leaves and exog- 
enous stem structure would certainly, if now discovered, be 
ranked among dicotyledons, even though in other characters it 
should resemble a monocotyledon, or differ from both classes. 
Assuming an ancestor with these two characters, monocotyle- 
dons must be considered as derived from a dicotyledonous stock, 
not necessarily at one epoch or from a single strain. Can indi- 
cations be found in the structure of living plants to suggest the 
conditions which operating for a length of time on such a stock 
might lead to the formation of a race or races essentially of the 
monocotyledonous type? 
Beginning with the most general character and that which 
gives its name to the class, we may ask: Under what circum- 
stances is the possession of a single cotyledon in place of two an 
advantage to the plant? An answer to that question is naturally 
sought among the few dicotyledons which possess but one seed 
leaf. I have compiled a list of species with this character. 
3The forms to which I refer are liliaceous: Anemarrhena, Albuca, and others 
Nearly allied to these very distinct genera both in mature and in seedling characters. 
I believe them to be primitive among the Liliaceae after making a careful compara- 
tive study of seedlings from forty-five genera of that family. Systematists differ as 
to the position of the Liliaceae among monocotyledons Some believe the type to 
be an ancient one from which many simpler monocotyledons are derived by reduc- 
tion. My observations on the structure of seedling monocotyledons from a number 
of families incline me to accept this view, and on gen 
attribute simplicity of structure when found in such advanced types 
Sperm to reduction rather than antiquity. Anemarrhena and Albuca, then, 
itive among the Liliaceae are primitive also among monocotyledons in general, 
™“SaRGANT, E.,/. c:, p. 76. 
