from The Century Dictionary.
- noun In botany, the multiplication, by congenital division, of an organ which is ordinarily entire.
- noun In geometry, a number associated with a place which indicates how many different places it contains, such that a particle could not by an ordinary motion within it pass from one to another.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Bot.) The separation of a leaf or floral organ into two more parts.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun botany The
separationof a leafor floral organinto two more parts.
from Wiktionary, Creative Commons Attribution/Share-Alike License
The French botanists, following Dunal and Moquin, attribute an increase in the number of whorls in the corolla, and other parts of the flower, to a process which they call chorisis, and they consider the augmentation to be due to the splitting of one petal, for instance, into several; -- somewhat in the same manner as one may separate successive layers of talc one from the other.
It is probably the idea of splitting or dilamination involved in the word chorisis that has led many English botanists to hesitate about accepting the notion.
Some of these cases may be accounted for by chorisis or by a cleavage of the original cotyledons, as happens, according to Duchartre,  in some Coniferæ, which he considers to be improperly termed polycotyledonous.
This duplication may either be accounted for on the theory of chorisis above alluded to, or by supposing that the extra corolline whorl is due to a series of confluent petalodic stamens; that the latter is the true explanation, in certain cases at least, is shown by some flowers of
Whether the additional organs in this last case are the result of complete lateral chorisis or of multiplication proper I do not know.
In these cases, owing to the non-development of the internodes, the nascent leaves are closely packed, and the conditions for adhesion are favorable, but in most of the so-called cases of adhesion of leaf to leaf by the surface, a preferable explanation is afforded either by an exuberant development (hypertrophy) or by chorisis (see sections on those subjects).
The truth would rather seem to be that, in the so-called parallel chorisis at least, the process is one of hypertrophy and over-development rather than of splitting.
Another very common mode of doubling is brought about by a real or apparent augmentation in the number of petals, as by multiplication, fission, or chorisis.
The deviations from the customary arrangement have been very generally attributed to suppression, or to chorisis.
This is probably due to a lateral chorisis or subdivision of the primitive tubercle or growing point, followed by a like subdivision of the vascular bundle supplying it.