23
SECTION IV.—Nature of the ovary and origin of the ovule in
Cannabis.
Discussion of contending theories. —The nature of the female ovary has, as
already explained, given rise to several theories. Some authors hold that
primarily the ovary is monocarpellary, others that primarily it is 2-carpellary, but
most who hold the second view admit that one of the carpels becomes abortive ; all
agree that the solitary carpel, or the persistent carpel if there be originally two, is
anterior. Still others hold that the ovary is not properly referable to the leaf-type
of organs, but is a quid sui generis, neither truly appendicular nor truly axial.
The nature of the ovule has also been equally in dispute, some of the theories
postulating for it an epicarpellary, others a hypocarpellary or truly axial origin.
It is necessary to examine these theories in detail before offering a substitute.
The first author, so far as the writer can find, who has attempted to elaborate a theory
on the subject is B. Clarke. 1 " The two stigmas," according to this author, " are anterior
" and posterior to the central point of the axil." This observation is very accurate ; as
already explained, the primary planes of orientation of the styles of the two flowers in the
axils of a pair of stipules intersect in the floral axis that occupies the axil of the leaf or
bract to which their stipules belong (PLATE 2, fig. 6). " The seed is pendulous, with a
" superior radicle, which is always on the external side of the ovary directly away from the
" axil laterally, the cotyledons being on the axillary side." This also is quite accurate.
" In its early stages the ovule appears to be pendulous from the apex of the cell, but in the
" ripened seed the attachment inclines distinctly to the posterior side, though less so than in
" HumuIus." As a matter of fact the small plug of less differentiated tissue in the carpellary
wall that corresponds to the attachment of the ovule is just posterior to the apex of the
cell—the point of origin of the posterior style—at all stages of growth subsequent to the
closure of the ovarian chamber ; in the ovule, as in the seed, it is the micropyle and not the
chalaza that is immediately under the organic apex of the ovarian chamber. The point is
not, however, important since it does not invalidate, indeed it rather strengthens, Clarke's
theory. " On the internal side of the ovary, that is, next the central point of the axil, a
"thickened rib, somewhat grooved, extends from the attachment of the ovule to its base,
" which considering also the position of the radicle and its cotyledons is doubtless the pla-
" centa ; this rib appears as if consisting of two columns, whereas the rib on the opposite
"or external side of the ovary is single and acuminated and each of them is opposite a stigma.
" The structure of the ovary therefore is the same as that of Elatostemma and Morus and
" taken in connection with the cotyledons and radicle, leaves no doubt that the fertile carpel is
"always anterior." The two ribs here described by Clarke are indeed present and are easily
seen, and the posterior rib is, as he states, thicker than the anterior ; but this posterior
rib is certainly, so far as the writer's observations extend, never grooved and is undoubtedly
never 2-columnar (PLATE 2, fig. 16). This thickened posterior rib therefore does not in
reality bear out Clarke's theory that we have here a placenta composed of the two united
margins of a single carpellary leaf with, at the upper end of this placenta, an ovule of
foliar origin arising from it. In any case the placenta, so far as the histology, as apart
from the organogeny, of the ovary shows, is not linear, but consists of a tiny circular patch
1 Ann. & Mag. Nat. Hist. Ser. 2, vol. xi, p. 439 (1853).