INTRODUCTION. XXXV 
That teratology may serve the purposes of syste- 
matic botany to a greater extent than might at first 
be supposed becomes obvious from a consideration 
of such facts as are mentioned under the head of 
Peloria, while the presence of rudimentary organs, or 
the occasional appearance of additional parts, or other 
changes, may, and often do, afford a clue to the relation- 
ship existing between plants—a relationship that might 
otherwise be unsuspected. So, too, some of the altera- 
tions met with appear susceptible of no other expla- 
nations than that they are reversions to some pre- 
existing form, or, at any rate, that they are manifes- 
tations of a phase of the plant affected different from 
that which is habitual, and due, as it were, to a sort of 
allotropism. 
The mutations and perversions of form, associated 
as they commonly are with corresponding changes of 
function, show the connection between teratology and 
physiology—a connection which is seen to be the 
more intimate when viewed in the light afforded by 
the writings and experiments of Gertner, Sprengel, 
and St. Hilaire, and, in our own times, especially by 
the writings and experiments of Mr. Darwin, whose 
works on the ‘ Origin of Species,’ and particularly on 
the ‘ Variation of Animals and Plants under Domesti- 
cation’ comprise so large a collection of facts for the 
in the way above mentioned are made use of in the following pages. 
The inconsistency manifested by their use may be excused on the 
ground of ignorance of the true structure, and by the circumstance that 
in many cases facts alone are recorded without an explanation of them 
being offered. Moreover, it is desirable to act in conformity with the 
usual practice of botanical writers, and not to change established 
terminology, even if suspected to convey false ideas, until the true 
condition of affairs be thoroughly well ascertained by organogenetic 
research or other means. 
