166 
IOWA ACADEMY OF SCIENCE 
2. Place of tlie Araceae in the natural system : In their ‘ ‘ Morphology 
of the Angiosperms” Coulter and Chamberlain suggest a scheme of 
relationship for the various orders of Monocotyledons, which, when ex- 
pressed diagrammatically, may be represented as follows: 
Prehistoric 
Primitive 
Forms 
i i — — j 
Pandanales Helobiales Graminales 
Palmales Synanthales Arales Farinales 
Llliales 
! 
Orchidales 
Scitaminales 
In this scheme of descent, the Aroids are placed next to the Helobiales, 
which they strongly resemble in many ways, with the suggestion that 
the latter are probably the more primitive and that the Aroids may be 
derived from them. In venation, Acorns and Gymnostachys strongly re- 
mind one of the Potomagetons and in their general habit of growth, 
branching, venation, inconspicuous spathe, and deficient endosperm, 
Pothos and Pothoidhim remind one of the same genus. In fact, the 
general impression left on one’s mind after such a comparison is that 
the Aroid is a Pondweed that has taken to the land. Possibly the 
aquatic habit is more primitive than the terrestrial, and doubtless also 
the anemophilous habit is more primitive than the entomophilous ; and 
from that standpoint it is perhaps reasonable to regard the Aroid as 
developed from some ancestral Naiad. On the other hand, it may not 
be impossible for terrestrial entomophilous plants to become aquatic and 
hydrophilous or anemophilous, and the poorly developed perianth of the 
Naiad may be an example of reduction from some better-developed form. 
It is safer merely to say that the two orders undoubtedly stand very 
close to each other, and represent together a common line of descent 
which has, in comparatively recent times, diverged in two directions. 
Beyond this cautious statement we can hardly go. 
The relationship existing between the Arales and Pandanales isi also 
a close one. The monoecious spadix of Typha, subtended by a spathe 
in the form of a bract, the spiral crowding of the blossoms:, the extremely 
reduced cyclic perianth, and the anatropous ovule with its abundant 
endosperm, all point to the existence of such a relationship. The hair- 
like perianth of the Pandanales can only be regarded as an example of 
