MORPHOLOGY. 485 
development, the persistent union of parts, usually 
separate in the adult state, has been traced to an 
arrest of the process of development, by no means 
necessarily coexistent with diminished growth. The 
diminished or increased number of parts is, in like 
manner, attributable to analogous causes, as also are 
the variations in arrangement and form, spoken of 
under the heads of Displacement, Peloria, Substitu- 
tion, &c. 
In the instance of displacements, it has been shown 
how slight a change is required to transform the so- 
called inferior ovary into a superior one. A defective 
development of the top of the flower-stalk in some 
cases, in others a lack of union between the tube of 
the receptacle or of the calyx (comprising in those 
terms not only the apex of the receptacle, but the base 
of the sepals) and the carpels, suffice to brig about 
this change in a character which for systematic pur- 
poses is of great value. 
Law of alternation—The circumstances that interfere 
with the law of alternation may be briefiy alluded 
to. The deviations from the customary arrangement 
have been very generally attributed to suppression, 
or to chorisis. It is unquestionable that either of these 
affords an efficient explanation of the arrangement in 
question, as also does that modification of chorisis, as 
it may be considered, which has been treated of under 
the head of Enation. Spiral torsion of the axis would 
likewise bring about analogous results. Still, it is quite 
conceivable that opposition or superposition of organs 
may occur without the intervention of any such opera- 
tions. This will be the more readily conceded when 
it is remembered that the phyllotaxis of leaves not 
unfrequently varies on different branches of the same 
individual tree, and that a similar variation in the 
flower would at once disturb the customary alter- 
nate arrangement. Coalescence of the vascular 
bundles in an unusual manner, and an irregular dis- 
