428 BOTANICAL GAZETTE [JUNE 
for the members are unlimited in number and have no ideal nature or 
limitations to be consulted. 
THIRD, the principal of fwsctional domination in metamorphosis, 
that is, it is function which takes the lead and structure follows. It 
is of course true that function and structure are reciprocally related ; 
there are cases where structure determines function; there are other 
cases in which non-functional factors, especially an aggregation of 
them, may outweigh a functional factor ; ‘nevertheless, it must be true 
that in a broad way it is function which determines structure, function 
often hampered, and even sometimes thwarted by other influences it is 
true, but function dominant in the long run. If this is not true, 
adaptation is but an accident if not a myth, and our whole idea of it 
but a vain vaporing of the imagination. This principle in general is 
necessary to both systems of morphology, but it is more prominent in 
realistic than in idealistic discussions. 
Fourth, the principle of indeterminate anatomical plasticity, that is, 
in all anatomical characters (size, shape, number, position, color, cellu- 
lar texture) plant-organs, or, if one pleases, plant-members, are not 
limited by anything in their morphological nature, but, under proper 
influence, may be led to wax and wane indefinitely in any of these 
respects. Of course this plasticity is hampered by innumerable prac- 
tical considerations, and by many hereditary “tendencies,” and many 
generations may be (though they are by no means always) necessary 
to produce a marked and permanent result; but the point is that lim- 
itations to anatomical plasticity do not come from the morphological 
nature of the part concerned. The principle may also be stated thus, 
that there is no causal relationship whatever between morphological 
nature and anatomical structure; stipules are usually smaller than the 
leaves they accompany and markedly different in form; yet they may 
become as large as the leaves and indistinguishable from them (as in 
Galium), or much larger, as in some Leguminosae ; there is obviously 
therefore nothing in the nature of a stipule as such to limit its size or 
shape; that it is usually smaller than its leaf is a purely functional and 
non-morphological matter. So, stems may lengthen immensely as in 
climbers or shorten to apparent disappearance as in rosette-plants, and 
so on with all other parts. This principle is equally true for both 
systems of morphology, and is perhaps the most clearly recognized of 
them all. 
Firtu, the principle of metamorphosis along lines of least resistance, 

