Abortion of the receptacle.—Here may be mentioned those cases of flowers with habitually inferior ovary (real or apparent), in which the receptacle fails, from some cause or other, to dilate as usual. This has already been alluded to under the head of Prolification, Displacements, &c. (pp. 78, 130, &c., figs. 35–37, 64, &c.), and hence requires only incidental comment in this place. There are, however, certain other cases of a similar nature which may here be referred to; such as the abortive condition of the inferior ovary, or rather of the receptacle, that usually encircles the ovary in Compositæ and Umbelliferæ. In the former natural order the following plants have been met with in this condition:—*Tragopogon pratense!, *Cirsium arvense, Hypochæris radicata, Senecio vulgaris!, Coreopsis Drummondi. In the latter order, Daucus Carota! Œnanthe crocata! and Thysselinum palustre, seem most frequently to have been observed in this state.[525] In some gourds the receptacle may be seen partially developed only, and forming a kind of cup, from which the true carpels protrude.
Abortion of the leaves.—Arrest of growth in the leaves occurs in different ways; sometimes the whole leaf is smaller than usual; at other times certain parts only are reduced in size; while, in a third class of cases, portions of the leaf are entirely suppressed.
Moquin[526] mentions having seen the leaves of Chenopodium vulvaria, and of Diplotaxis muralis reduced to a fourth of their natural size; and he alludes to other cases of the same nature, seen by other observers, in Hypericum perforatum and Blitum polymorphum.
Nicandra physaloides[527] has also been met with in a similar condition, which, indeed, is a common result of insect-puncture, and of fungous growth in plants. Those instances in which the leaf is diminished in size, without any attendant malformation in other organs, may be regarded rather as variations than as monstrosities, as in the case of the entire-leaved varieties of those plants which ordinarily have cut or divided leaves, e.g. Plantago Coronopus, var. integrifolia, Papaver Rhœas integrifolia, &c. &c. The same remark may be made of those specimens in which one part of the leaf is developed to a less extent than another, as happens in the submerged leaves of such plants as Ranunculus aquatilis, Cabomba aquatica, the spiney leaves of Berberis, the fenestrated leaves of Ouvirandra, &c. In the illustrations last cited the relative deficiency of one portion, as contrasted with another, takes place as a constant occurrence, and is uniform and regular throughout the whole leaf. When, on the other hand, the deficiency in question happens accidentally and irregularly, the change may be considered as a malformation. One side of the blade of the leaf is frequently affected in this manner, the other portions remaining unaffected. It would appear as if any plant might be thus altered, but the following species appear to be particularly subject to this change: Æesculus Hippocastanum, Digitalis purpurea, Morus alba, Fagus silvatica contracta (hort.), Codiæum variegatum var. erosum (hort.), Broussonettia papyrifera, Scolopendrium vulgare, &c.
Frequently this irregular diminution in proportion is coexistent with an unusual degree of cleavage or laciniation of the margin, as in Acer platanoides laciniatum, Tilia asplenifolia, Alnus imperialis (hort.), Fagus silvatica var. (hort.), &c.
In the case of what are sometimes termed interrupted leaves, the laminar portions of the leaf are here and there deficient on both sides of the midrib, leaving small portions of the latter, as it were, denuded and connecting the segments of the laminæ one with the other. This has been observed amongst other plants in Veronica latifolia, Broussonettia papyrifer, Codiæum variegatum var. interruptum (hort.), Scolopendrium vulgare, &c.[528] ([See p. 328.])
In some of the leaves which have been already referred to in illustration of the inordinate growth of the cellular portions, the increased development of parenchyma is associated with a contracted state of the midrib and its branches, producing a puckered appearance of the leaf, an exaggerated degree of that change which produces what are termed "folia bullata." In illustration may be cited various species of Mentha, Perilla, Coleus, Fagus silvatica crispa, Cytisus, Laburnum var., and other forms, cultivated in gardens for their singularity.
Entire absence of the stalk of the leaf occurs normally in sessile leaves; on the other hand the blade of the leaf is only occasionally developed in the phyllodineous Acacias, in some species of Oxalis, Indigofera, Lebeckia, Ranunculus, Bupleurum, &c.
De Candolle,[529] from a consideration of Strelitzia juncea, in which the petiole alone is developed, was led to the inference that in many monocotyledonous plants the blade of the leaf was never developed, the portion present being the sheath or stalk, unprovided with limb. The correctness of this inference is shown, amongst other things, by the occasional presence of a leaf-blade in Strelitzia juncea itself.