CLASSIFICATION. 489 
Take the characters of exogens as distinct from 
endogens ; even under ordinary circumstances, no abso- 
lute distinction can be drawn betweenthem. There are 
plants normally of an intermediate character, while, to 
take exceptional instances, there are exogens with the 
leaves and flowers of endogens, and endogens whose out- 
ward organisation, at any rate, assimilates them to exo- 
gens. Diclinous or monochlamydeous plants owe their 
imperfect conformation to suppression, and may become 
structurally complete by a species of peloria. Struc- 
turally hermaphrodite flowers become unisexual by 
suppression, or are rendered incomplete by the non- 
development of one or more of their floral whorls. 
Hypogynous flowers become perigynous by adhesion, 
or by lack of separation; perigynous ones become 
hypogynous by an early detachment from the recep- 
tacle that bears them, or by the arrested development 
of an ordinarily cup-like receptacle. 
How the relative position of the carpels and the 
calyx may be altered has already been alluded to, as has 
also the circumstance that while it 1s common to find 
an habitually imferior or adherent ovary becoming 
superior or free, it is much more rare to find the 
superior ovary adherent to the receptacle or to the 
ealyx.' Regular and irregular peloria, too, serve 
to show how slight are the boundaries, not only 
between different genera, but also between different 
families. 
While, therefore, teratology may be an unsafe guide 
in strictly artificial schemes, it 1s obvious that its 
teachings should have great weight in all philosophical 
systems of classification. 
The questions will constantly arise, does such and 
such a form represent the ancestral condition of certain 
plants? Is it a reversion to that form? or is it, on 
the other hand, the starting point of new forms ? 
1 An illustration of this latter nature in the case of a cherry, yhich 
was surmounted by the calyx lobes, precisely as in the case of a ; tha. 
ceous fruit, has been given at p. 424, adnot. 
