formation can readily be
found. Under each subdivision will be found general explanatory remarks,
illustrative details, and usually a summary of the more important facts
and the inferences to be derived from them. Bibliographical references
and lists of the plants most frequently affected with particular
malformations are also given. In reference to both these points it must
be remembered that absolute completeness is not aimed at; had such
fullness of detail been possible of attainment it would have
necessitated for its publication a much larger volume than the
present.[5] It is hoped that both the lists of books and of plants are
sufficiently full for all general purposes.[6]

In the enumeration of plants affected with various malformations the !
denotes that the writer has himself seen examples of the deviation in
question in the particular plant named, while the prefix of the *
indicates that the malformation occurs with special frequency in the
particular plant to which the sign is attached.

Teratological alterations are rarely isolated phenomena, far more
generally they are associated with other and often compensatory changes.
Hence it is often necessary, in studying any given malformation, to
refer to two or more subdivisions, and in this way a certain amount of
repetition becomes unavoidable. The details of the several cases of
malformation given in these pages are generally arranged according to
their apparent degree of importance. Thus, in a case of prolification
associated with multiplication of the petals, the former change is a
greater deviation from the customary form than the latter, hence
reference should be made, in the first instance, to the sections
treating on prolification, and afterwards to those on multiplication. To
facilitate such research, numerous cross references are supplied.

In the investigation of teratological phenomena constant reference must
be made to the normal condition, and _vice versa_, else neither the one
nor the other can be thoroughly understood. It cannot, however, be
overlooked that the form and arrangement called normal are often merely
those which are the most common, while the abnormal or unusual
arrangement is often more in consonance with that considered to be
typical than the ordinary one. Thus, too, it is often found that the
structural arrangements, which in one flower are normal, are in another
abnormal, in so far that they are not usual in that particular instan