cumstances, may be referred to in illustration
of this occurrence, while the adventitious spurs on the calyx of some
monstrous flowers seem due also to a like cause. These have already been
alluded to at p. 315.

=Enation from the corolla.=--The instances of this are more frequent
than in the case of the calyx, and admit of classification according as
they occur in polypetalous or gamopetalous flowers, on the outer or
inner surface of the petals, &c. Under natural circumstances the
formation of scales, lobes, &c., from the petals, as in some
_Caryophylleae_, _Sapindaceae_, &c. &c., may be explained, as already
remarked, by this process, rather than by fission, chorisis, or by
substitution of petals for stamens, &c. Each case must, however, be
examined on its own merits, as it is not safe to decide upon the
arrangement of parts in one flower by simply referring to the analogy of
others. In the following illustrations the course of development has
not, in all cases, been observed, and hence the explanation here given
must be taken with some reserve; for should it prove that the
adventitious lobes, &c., are formed simultaneously with the ordinary
petals, the case will be one of chorisis rather than of enation, as here
understood. Again, it may be that the supernumerary organs really
represent petals or stamens in disguise, though this hypothesis demands
the further assumption (in order to account for the interference with
the law of alternation) that suppression of certain organs has taken
place.

Taking first those instances in which the supplementary petals appear on
the inner surface of the corolla, as being at once the most frequent,
and as presenting the closest analogy, with similar conformations, under
natural circumstances, certain double-flowered varieties of the Chinese
primrose, _Primula sinensis_, may be mentioned. In these flowers the
calyx is normal, the tube of the corolla is traversed by ten vascular
bundles, and the limb is divided into ten fimbriated lobes. About
halfway up the tube, on the inner surface, are given off five
supernumerary petals, opposite to as many lobes of the corolla. Some of
the supplementary petals have a stamen in front of them, in the same
relative position as in the normal flower. In some cases the back or
outer surface of the supplementary petal is turned towards the inner or
upper surface of the primary corolla, thus [Symbol: ((turned 90 degrees
cw]; while, in other instances,