1904] SARGANT: EVOLUTION OF MONOCOTYLEDONS 341 
supposing its single cotyledon to bea terminal leaf—a difficulty 
so formidable that the supporters of its terminal character have 
been obliged to assume that cotyledons are not true leaves, but 
organs sw generis. Their structure lends no support to this view. 
The other characters which separate monocotyledons from 
dicotyledons are by no means so constant as the three already 
discussed ; namely, the single cotyledon, the stem-anatomy, and 
the development of the embryo. Parallel venation of leaves, 
short duration of the primary root, and albuminous seeds are 
characters neither universal among monocotyledons nor confined 
to them. They are found in geophilous plants of both classes, 
though far more general among monocotyledons. 
The value of these three subordinate characters as evidence in 
favor of the geophilous origin of monocotyledons is somewhat 
lessened by the consideration that they are found mainly —not 
exclusively —among geophilous genera within that class. They 
may be considered direct adaptations to the mode of life adopted 
by the species of their more recent ancestors, rather than an 
inheritance from geophilous ancestors common to all monocoty- 
ledons. The presence of all three characters among the palms, 
however—a family composed exclusively of trees—cannot be 
explained by recent adaptation to geophily. I shall return 
shortly to the evidence for the descent of all palms from a 
Seophilous ancestor. 
The trimerous symmetry of the flower is a very important 
character of monocotyledons, particularly to those botanists who 
derive the simpler flowers of the Aroideae, Gramineae, Palmae, 
and other orders from the more elaborate, considering their 
simplicity as due to the reduction of the floral parts. But I can 
discover no grounds for considering the trimerous flower as an 
adaptation to geophily. There may be an unsuspected connec- 
tion, or the prevailing floral symmetry of monocotyledons may be 
an inheritance from the ancestral stock. A trimerous calyx and 
Corolla is not uncommon among the Ranales. 
To sum up, of the seven characters mentioned as distinguish- 
ing monocotyledons from dicotyledons, four have been shown to 
