Floral Evolution. 
79 
Symmetry. 
Perianth. 
Andrcecium. 
Gyn^ecium. 
Magnoliaceae 
Spiral 
CO 
CO 
CO 
Anonaceae 
Ranunculaceae 
Hemic yclic 
3 + 3 + 3 
Definite 
CO 
CO 
Menispermaceae 
Cyclic 
3+3+3+3 
3 + 3 
3 
Berberidaceae 
Cyclic 
3+3+3+3 
3 + 3 
1 
Moreover, the working of the same principle of economy is 
observable, in many cases, in the series of genera comprising each 
natural order of Ranales. 
Let us n:w examine briefly the broad biological significance of 
this principle of progressive economy in production of parts. 
General decrease means decrease in the number of male and 
female organs, and therefore, ceteris paribus, a decreased chance of 
pollination. But natural selection would clearly not permit of any 
interference with the efficient performance of one of the principal 
vital functions ; the result is that a second principle has been 
called into operation in order to make possible the economy of the 
first one, ensuring that an increased chance of pollination, rather 
than the reverse, shall accompany the general tendency to 
oligomery. This second principle we may name the tendency to 
2. Progressive Adaptation to Insect Visitors. 
From a general study of the various floral types, it is gathered 
that these two are the fundamental tendencies in the evolutionary 
history of the flower, and we hope to illustrate their working in the 
sequel. 
First, however, attention must be called to one or two im¬ 
portant tendencies which subserve the two fundamental principles 
named. 
(a). In the first place we have the well-recognized tendency 
to increased conspicuousness either (a) by enlargement of the 
individual flower, or (b)—and this is the more wide-spread—by the 
aggregation of flowers into progressively dense inflorescences by 
active branching of the floral axes. The first experiment, so to 
speak, in the direction of increasing conspicuousness is reflected in 
the petaloid perianth, which represents one of the principal steps 
