The pistil, too, is necessarily subject to very grave alterations when affected with this malformation. It is separated into its constituent carpels; and these assume a leaf-like aspect, and are in the great majority of instances destitute of ovules. Indeed, virescence or chloranthy is very intimately connected with this aberration, as might have been anticipated, for if the parts of the flower assume more or less of the condition of stem-leaves or bracts, it is quite natural to expect that they will partake likewise of the attributes of leaves, even at the expense of their own peculiar functions.
It occasionally happens that an adventitious bud arises from the axil of a monocarpellary pistil. This takes place sometimes in Leguminosæ, and seems to have been more frequently met with in Trifolium repens than in other plants. The species named is, as is well known, particularly subject to a reversion of the outer whorls of the flower to leaves, and even to a leaf-like condition of the pistil. There are on record instances wherein a leaf-bud has been placed in the axil of a more or less leaf-like carpel; while at other times a second imperfect carpel has been met with in the axil of the first.[140] I have myself seen numerous imperfectly developed cases of this kind.
It may be asked whether such cases are not more properly referable to central prolification—whether the axis is not in such flowers terminated by two, rather than by one carpel? It is, however, generally admitted by morphologists that the solitary carpel of Leguminosæ is not terminal, but is the sole existing member of a whorl of carpels, all the other members of which are suppressed as a general rule, though exceptional instances of the presence of two and even of five carpels have been described.[141]
Again, the adventitious bud or carpel is placed, not laterally to the primary one, or opposite to it, on the same level, but slightly higher up—in fact, in the axil of the primary carpellary leaf. Griffith figures and describes[142] an instance of the kind in a species of Melilotus. The stalk of the ovary is mentioned as having a sheathing base, bearing in its axil a prolongation of the axis of inflorescence, in the form of a short spike with hairy bracts and imperfect flowers, the latter having a well-formed calyx and rudimentary petals and stamens. Griffith infers, from this specimen, that the legume is not to be considered as a terminal leaf.
List of Genera in which Axillary Prolification has been observed.
