founded on the Structure of their Seedlings. 83 
Absence of a true Epidermis in the Root above the Root- 
sheath. 
This character of the root is so far as we know universal 
among Monocotyledons, but not confined to them. It is found 
in the Nymphaeaceae among Dicotyledons. I can form no 
guess as to its origin. 
Parallel Venation of the Leaves . 
Parallel venation is general among the leaves of Mono- 
cotyledons, but by no means universal. Professor Areschoug 
has remarked that the linear leaves characteristic of most 
bulbous Monocotyledons are better adapted to push upwards 
through the soil than any Dicotyledonous type of leaf ( 3 , p. 55). 
The bulb seems in many respects to be the most highly 
specialized form of geophyte: its squat axis and pointed 
leaves with their broad sheathing base are clearly adaptations 
to a geophilous life. The anatomy of the stem and the short 
life of the roots are characters correlated with those just 
mentioned. 
The Ternary Symmetry of the Flower. 
The three-whorled flower is very generally found among 
Monocotyledons, but is not universal. Many of the exceptions 
may be derived from it by reduction (Aroideae). No connexion 
between this symmetry and a geophilous habit occurs to me, 
except that the parts of the flower may perhaps pack easily 
into a bud when arranged in this way. 
The presence of an Endosperm in the Seed. 
This character is neither universal among Monocotyledons 
nor confined to them, but it is much more common in this 
class of plants than among Dicotyledons. I believe it to be 
a character common to the majority of highly specialized 
geophytes. This is illustrated by the fact that among the 
twenty-seven Dicotyledonous genera mentioned in Tables I 
and II, three only ( Card amine, Serratula , and Pinguicula ) 
