The corolla may be hypertrophied in some cases, though the change is more rare than in most other organs. Moquin-Tandon mentions as subject to this anomaly species of Galeopsis, Prunella, Scabiosa, and Dipsacus, and also mentions a remarkable variety of Viola odorata cultivated in the neighbourhood of Toulouse. The same learned author also alludes to the so-called double Composites, viz. those in which the usually tubular florets of the disc assume the form and proportions of those of the ray, but these are hardly cases of hypertrophy.
Enlargement of the andrœcium.—Dunal[500] alludes to a curious instance in a species of Verbascum, the lower flowers of which had hairy stamens as usual, but the filaments of the topmost flower were quite destitute of hairs, and dilated like a flat ribbon.
Moquin relates having found in the neighbourhood of Toulouse a plant of Solanum Dulcamara in which all the upper flowers had two or three stamens of larger dimensions than the others. This happens habitually in Solanum tridynamum and S. Amazonicum, and to a less extent in S. vespertilio and S. cornutum; also in some species of Hyoscyamus. These cases show the close affinity between the Solanaceæ and the Scrophulariaceæ.
Enlargement of the gynœcium.—In some flowers which have become accidentally female the pistil becomes unusually large, and even to such an extent as to prevent the passage of the pollen. Moquin remarks having seen this enlargement in the pistils of Suæda fruticosa and Kochia scoparia. The flowers of these Chenopods, under these circumstances, resemble the female flowers of some nettles. The styles of Anemone are also much enlarged as the result of cultivation, and from their petaloid appearance resemble those of the Iris (Goethe). MM. Seringe and Heyland[501] have figured some anomalous flowers of Diplotaxis tenuifolia in which the pistil, more or less distended and deformed, was considerably elongated below, so that it seemed to be borne upon a long stalk, analogous to that of fruits of Capparids. Dr. Klinsman[502] mentions an instance of a similar kind combined with hypertrophy of the sepals and pistils; indeed, the alteration is not uncommon among Crucifers. Pyrethrum inodorum is very subject to hypertrophy. The styles of its radial florets become elongated without any other alteration; at the same time the small corollas become green, and show a tendency to assume a foliaceous condition. Sometimes the hypertrophy affects also the styles of the central florets, and these also become enlarged to double or treble their usual dimensions.
Linné has remarked that the ovary of Tragopogon sometimes assumes very large dimensions, as also does the pappus. He mentions a double-flowered variety, the ovaries of which become ten or twelve times larger than ordinary. M. Clos[503] records an instance in Rumex scutatus wherein the pistil was hypertrophied or club-shaped, and open at the top, or in other cases funnel-shaped, three-lobed at the summit, each lobe terminated by a style. One of the most frequent causes tending to the hypertrophy of the pistil is attributable to the puncture of insects; thus, when the ovary of Juncus articulatus is thus punctured, it acquires a size two or three times larger than ordinary, becoming at the same time sterile.[504]
Occasionally the enlargement may be due to a fusion or incorporation of other elements; thus, M. Lemaire describes an instance in which the style of Sinningia purpurea was much larger than ordinary, tubular, bearing three small lobes, and altogether bearing much resemblance to the column or "gynosteme" of Orchids. This appearance was due to the cohesion and intimate union of the styles with three abortive stamens.[505]
Enlargement of the fruit.—Most cultivated fruits are in a state of true hypertrophy. Girod de Chantrans, after many trials, succeeded in producing a peculiar variety of pea with pods double the ordinary size.[506] M. Clos[507] mentions a case wherein the carpels of Delphinium dictyocarpum were hypertrophied. The change in size may or may not be attended by a difference in form; thus, in certain Leguminosæ, as Medicago lupulina, Melilotus leucantha, the carpels are sometimes hypertrophied and elongated, so as to resemble a claw or hook.[508]
The fruit of the common groundsel (Senecio vulgaris) is in its normal condition two or three times shorter than the involucre, and cylindrical for its whole length, but it frequently happens that the fruits become as long as the involucre itself, and taper from the base upwards, so as to become beaked. Under this head may also be mentioned the fleshy bulbils that are found in the capsules of Crinum, Amaryllis, and Agave. These are true seeds enormously dilated.[509] In these seeds the outer coating becomes very thick and fleshy, and is traversed by spiral vessels.
It is obvious that very important results in a practical point of view may be and have been arrived at by cultivators availing themselves of this tendency of plants to increase in dimensions under certain circumstances. It is needless to do more than refer to the many fruits, vegetables, and cereals, which have thus become enlarged and improved by careful selection and rearing.
Alterations of consistence often accompany changes in size. The change may be one whereby the tissues become unusually hardened, by the excessive formation of secondary woody deposits, or softer and more succulent than ordinary, from the formation of an inordinate amount of loose cellular tissue. Generally speaking, the appearances presented in such cases are not sufficiently striking to demand notice other than as regards their size. One illustration, however, may be cited from its singularity. This was the case of a dahlia, in which the centre of the flower was occupied by a projecting knob as large as a walnut, brown in colour, and very hard in texture. This knob was nothing but the enlarged and indurated extremity of the common receptacle, destitute of the scales and florets which usually spring from it. No insect-puncture could be detected, and no other reason for this peculiarity could be ascertained.