24
of less differentiated tissue. Apart, however, from this, Clarke's theory fails to explain
why there are two styles, and particularly why the posterior one, where by his interpreta
tion there is no carpel at all, should be longer and stronger than the anterior, which belong
to the only carpel that he admits. Clarke's careful attempt, from organographic considera
tions alone, to interpret the structure of the ovary and the origin of the ovule, cannot therefore
be accepted as successfully explaining all the conditions.
The next important attempt to explain the structure of the ovary in Cannabis we owe
to Payer.1This author states that the ovary commences as two carpels, at first distinct,
but afterwards united at the base and forming two styles. At the base of each carpel
there is a depression ; of these, the posterior soon becomes entirely obliterated while the
anterior becomes enlarged and forms the solitary loculus of the ovary. The ovule he claims
as internal and axial. When the ovule appears, the loculus is not very deep and the ovule
does not quite fill the cavity ; it is thereafter carried up by intercalary growth to the apex
of the loculus, the primine and the secundine being developed during its transit. Compar-
ing the Cannabineæ with the Tremandreæ, Payer says that as regards the ovary they
differ only in this, that whereas in the Tremandreæ there are two carpels, both lateral
to the axis, and each forming a loculus, in the Cannabireæ only one of the carpels, the
anterior, is lateral to the axis and forms a loculus ; the posterior remains as a rudimentary
structure at the apex of the axis and does not form a loculus.
This must mean, if it means anything, either that the axis continues to grow upward
carrying on its apex the ovule and, just behind the ovule, the internal style ; or, if the apex
of the axis remains stationary, that the anterior carpellary loculus progressively deepens so
that its base gradually leaves the two styles and the solitary ovule behind. In either case
the posterior aspect of the ovarian wall—the part corresponding to B. Clarke's 'placenta'
—should be of axial origin.
However, from what Briosi and Tognini 2 have shown, Payer's theory does not accord
so well with reality as do his drawings. He speaks of two carpels as appearing before
the ovule ; he shows a small central swelling round which a circular cushion of tissue
develops, from the margins of which subsequently arise the two out-growths—one behind,
the other in front—that become ultimately the larger posterior and smaller anterior styles.
The cavity of the loculus too remains open at the top till a comparatively late stage, a
fact that is confirmed in the drawings of Briosi and Tognini ; this is quite at variance with
Payer's theory, which postulates the union of his two carpels before the growth of the
posterior one becomes aborted—presumably therefore before the amplification of the loculus
formed by the depression at the base of the anterior carpel has much more than com-
menced. The Italian botanists also find that the ovarian chamber is closed and the
solitary ovule has reached its final position just behind the apex of the loculus, before
the ovular integuments appear, whereas Payer's figures make the appearance of these
integuments antecedent to the closing of the ovarian chamber and contemporaneous with a
passage upward of the ovule along the posterior wall of the ovary. But, if the posterior
side of the ovarian wall is of axial nature, there can be no such passage up that wall. The
ovule was at the posterior side of the apex to begin with, and must have continued to be
there all along, whether the axis grew upwards by intercalary growth or the anterior
carpel became hollowed out downwards.
Payer's theory succeeds in explaining the origin of a posterior as well as an anterior
style, and to this extent is more satisfactory than that of Clarke. But it does not explain
why the style belonging to the abortive posterior carpel should be larger than that of
1 Traité d'organogénie comparée de la fleur, p. 281 (1857).
2 Intorno all' anatomia della Canapa, p. 57.