CLASSIFICATION. 489 



Take the characters of exogens as distinct from 

 endogens ; even under ordinary circumstances, no abso- 

 lute distinction can be drawn between them. 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 is common to find 

 an habitually inferior or adherent ovary becoming 

 superior or free, it is much more rare to find the 

 superior ovary adherent to the receptacle or to the 

 calyx.^ Regular and irregular peloria, too, serve 

 to show how slight are the boundaries, not only 

 between diff'erent genera, but also between different 

 families. 



While, therefore, teratology may be an unsafe guide 

 in strictly artificial schemes, it is 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 ? 



' An iUusti-ation of tliis latter nature in the case of a cherry, which 

 was surmounted by the calyx lobes, precisely as in the osvso of a poma- 

 ceous fryit. has been given at p. 4lll, nduof. 



