336 BOTANICAL GAZETTE [MAY 
geophytes. Their originally distinct cotyledons become more 
and more closely united in order to economize material. In the 
end a single cotyledonary member is formed by their complete 
fusion. A monocotylous race might easily be derived in this 
way from one with two cotyledons. 
But monocotyledons are distinguished from dicotyledons by 
other characters besides the single seed leaf. Taking these 
characters one by one, are they consistent with the hypothesis 
that monocotyledons were derived from a stock of dicotylous 
angiosperms by adaptation to the geophilous habit? 
As has been said (p. 332), there are independent grounds for 
believing that monocotyledonous stem anatomy is derived from 
that of an ancestor framed on the dicotyledonous type. Modi- 
fication of the ancestral stem structure in this direction might 
well follow on the gradual assumption by succeeding generations 
of the geophilous habit. For in every plant which passes part 
of the year underground a large foliage bud is formed on the 
subterranean stock in the course of a growing season, and this 
bud after remaining quiescent through the bad weather will push 
up as the next period of growth approaches. Such buds are 
formed even in the least specialized geophytes. 
Scale leaves form the outer covering of such a bud; then 
follow the radical leaves which sometimes, but not always, sur- 
round the rudiment of an erect stem which will bear flowers as 
well as leaves. Scale leaves and radical leaves alike are broad- 
based; the insertion of each on the squat axis occupies a con- 
siderable segment of its circumference. When growth begins 
with the first genial weather, the axis does not elongate, or those 
basal internodes, at any rate, are suppressed which separate the 
whorls of scale leaves and of radical leaves from each other. 
The traces which enter the axis from those leaves fall naturally 
into concentric circles within it. In fact, they are at once 
arranged like the leaf traces of a monocotyledonous stem. 
In many geophytes the parenchyma of the axis becomes 4 
massive tissue packed with food stuff. This development of the 
tissue which surrounds them naturally tends to isolate the leaf 
traces from each other. The interfascicular cambium first dis- 
