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Fig. 9.—Eranthis hyemalis. Transition from flat sepal to tubular petal.

Like the petals, the stamens, and even the styles, assume a hollow tubular form. This change of form in the case of the stamens is, of course, usually attended by the petaloid expansion of the filament, or anther, and the more or less complete obliteration of the pollen sacs, as in Fuchsias, and in some double-flowered Antirrhinums.[20] So also in some semi-double varieties of Narcissus poeticus, and in Aquilegia. By the late Professor Charles Morren, this affection of the stamens and pistils was called Solenaidie,[21] but as a similar condition exists in other organs, it hardly seems worth while to adopt a special term for the phenomenon, as it presents itself in one set of organs.

In many of these cases it is difficult to say whether the cup-like or tubular form is due to a dilatation or hollowing out of the organ affected, or to a fusion of its edges. The arrangement of the veins will in some cases supply the clue, and in others the regularity of form will indicate the nature of the malformation, for in those instances where the cup is the result of expansion, its margin is more likely to be regular and even than in those where the hollow form is the result of fusion.

Cohesion of several organs by their margins:—leaves, &c.—The union of the margins of two or more different organs is of more common occurrence than the preceding, the leaves being frequently subjected to this change. Occasionally, the leaflets of a compound leaf have been observed united by their margins, as in the strawberry, the white trefoil, and others. Sometimes the union takes place by means of the stalks only. I have an instance of this in a Pelargonium, in Tropæolum majus, and Strelitzia regina; in other cases, the whole extent of the leaf becomes joined to its neighbour, the leaves thus becoming completely united by their edges, as in those of Justicia, oxyphylla.[22] M. Clos[23] has observed the same thing in the leaves of the lentil Ervum lens, conjoined with fasciation of the stem, and many other examples might be given. Some of the recorded cases are probably really due to fission of one leaf into two rather than to fusion. Although usually the lower portions of the leaf are united together, leaving the upper parts more or less detached, there are some instances in which the margins of the leaf at their upper portion have been noticed to be coherent, while their lower portions, with their stalks, were completely free.[24]

Cohesion of the leaves frequently accompanies the union of the branches and fasciation as might have been anticipated. Moquin cites the fenestrated leaves of Dracontium pertusum, as well as some cases of a similar kind that are occasionally met with, as instances of the cohesion of the margins at the base and apex of the leaf, which thus appears perforated. This appearance, however, is probably due to some other cause. When the leaves are verticillate and numerous, and they become coherent by their margins, they form a foliaceous tube around the stem. When there are but two opposite leaves, and these become united by their margins, we have a state of things precisely resembling that to which the term connate is applied.

Fusion of the edges of the cotyledons also occasionally takes place, as in Ebenus cretica.[25] It has also been observed in Tithonia, and is of constant occurrence in the seed leaves of some Mesembryanthema. This condition must be carefully distinguished from the very similar appearance produced by quite a different cause, viz., the splitting of one cotyledon into two, which gives rise to the appearance as if two were partially united together.

Some of the ascidia or pitcher-like formations are due to the cohesion of the margins of two leaves, as in a specimen of Crassula arborescens, observed by C. Morren.

Fig. 10.—Two-leaved pitcher of Crassula arborescens, after C. Morren.

The stipules may also be fused together in different ways; their edges sometimes cohere between the leaf and the stem, and thus form a solitary intra-axillary stipule. At other times they become united in such a manner as to produce a single notched stipule opposite to the leaf. Again, in other cases, they are so united on each side of the stem, that in place of four there seem only to exist two, common to the two leaves as in the Hop.

To the Rev. M. J. Berkeley I am indebted for specimens of a curious pitcher-like formation in the garden Pea. The structure in question consisted of a stalked foliaceous cup proceeding from the inflorescence. On examination of the ordinary inflorescence, there will be seen at the base of the upper of two flowers a small rudimentary bract, having a swollen circular or ring-like base, from which proceeds a small awl-shaped process, representing the midrib of an abortive leaf. In some of Mr. Berkeley's specimens, the stipules were developed as leafy appendages at the base of the leaf-stalk or midrib, the latter retaining its shortened form, while, in others, the two stipules had become connate into a cup, and all trace of the midrib was lost. The cup in question would thus seem to have been formed from the connation of two stipules which are ordinarily abortive.

Cohesion of the bracts by their edges, so as to form a tubular involucre, or by their surfaces, so as to form a cupule, is not of uncommon occurrence, under natural conditions, and may be met with in plants which ordinarily do not exhibit this appearance.

Cohesion of the sepals in a normally polypetalous calyx renders the latter gamosepalous, and is not of uncommon occurrence, to a partial extent, though rarely met with complete. I have observed a junction of the sepals to be one of the commonest malformations among Orchids, indeed such a state of things occurs normally in Masdevallia Cypripedium, &c. An illustration of this occurrence is given by Mr. J. T. Moggridge in Ophrys insectifera, in 'Seemann's Journal of Botany,' 1866, p. 168, tab. 47. In Orchids, this cohesion of sepals is very often co-existent with other more important changes, such as absence of the labellum, dislocation of the parts of the flower, &c.

Fig. 11.—Gamopetalous flower of Papaver bracteatum.

Cohesion of the petals.—Linnæus mentions the occurrence of cohesion of the petals in Saponaria.[26] Moquin notices a Rose in which the petals were united into a long tube, their upper portions were free and bent downwards, forming a sort of irregular limb. An instance of the polypetalous regular perianth of Clematis viticella being changed into a monopetalous irregular one, like the corolla of Labiates, is recorded by Jaeger.[27] There is in cultivation a variety of Papaver bracteatum, in which the petals are united by their margins so as to form a large cup. Under normal circumstances, the petals become fused together by their edges along their whole extent, at the base only, at the apex only, as in the Vine, or at the base and apex, leaving the central portions detached. Indications of the junction of the petals may generally be traced by the arrangement of the veins, or by the notches or lobes left by imperfect union. In Crocuses I have frequently met with cohesion of the segments of the perianth, by means of their surfaces, but the union was confined to the centre of the segment, leaving the rest of the surfaces free.

Cohesion of the stamens.—Under natural circumstances, cohesion of the stamens is said to take place either by the union of their filaments, so as to form one, two, or more parcels (Monadelphia, Diadelphia, Polyadelphia); at other times, by the cohesion of the anthers (Syngenesia), in which latter case the union is generally very slight. It must be remembered, however, that the so-called cohesion of the filaments is in many cases due rather to the formation of compound stamens, i.e. to the formation from one original staminal tubercle of numerous secondary ones, so that the process is rather one of over development than of fusion or of disjunction. These conditions may be met with as accidental occurrences in plants or in flowers, not usually showing this arrangement. Thus, for instance, Professor Andersson, of Stockholm, describes a monstrosity of Salix calyculata, in which the stamens were so united together as to form a tube open at the top like a follicle.[28] This is an exaggerated degree of that fusion which exists normally in Salix monandra, in Cucurbits and other plants.

Cohesion of the pistils is also of very frequent occurrence in plants, under ordinary circumstances, but is less commonly met with than might have been expected as a teratological phenomenon.

Further details relating to cohesion of the various parts of the flower are cited in Moquin-Tandon, 'El. Ter. Veg.,' p. 248; 'Weber. Verhandl. Nat. Hist. Vereins f. d. Preuss. Rheinl. und Westphal.,' 1860, p. 332, tabs. 6 et 7.

Formation of ascidia or pitchers.—In the preceding paragraphs, the formation of tubular or horn-like structures, from the union of the margins of one organ, or from the coalescence, or it may be from the want of separation of various organs, has been alluded to, so that it seems only necessary now, by way of summary, to mention the classification of ascidia proposed by Professor Charles Morren[29], who divides the structures in question into two heads, according as they are formed from one or more leaves. The following list is arranged according to the views of the Belgian savant, and comprises a few additional illustrations. Those to which the ! is affixed have been seen by the writer himself; the * indicates the more frequent occurrence of the phenomenon in some than in other plants. Those plants, such as Nepenthes, &c., which occur normally and constantly, are not here included. Possibly some of the cases would be more properly classed under dilatation or excavation.

Ascidia.

A. Monophyllous.

1. Sarracenia-like pitchers, formed by a single leaf, the edges of which are united for the greater portion of their length, but are disunited near the top, so as to leave an oblique aperture.

 *Brassica oleracea (several of the cultivated varieties)!

 *Tilia europæa!

 Pelargonium inquinans!

 Staphylea pinnata.

 Amorpha fruticosa.

 Pisum sativum!

 Lathyrus tuberosus.

 Vicia sp.

 Gleditschia sp.

 Ceratonia siliqua.

 Trifolium repens!

 Cassia marylandica.

 Mimosa Lophantha.

 Rosa centifolia.gallica.

 Begonia sp.

 Bellis perennis!

 Nicotiana sp.

 Goodenia ovata!

 Antirrhinum majus!

 Vinca rosea.

 Polygonum orientale.

 Aristolochia sipho?

 Codiæum variegatum var.!

 Spinacia oleracea.

 Corylus avellana!

 Polygonatum multiflorum.

 Xanthosoma appendiculatum!

2. Calyptriform or hood-like pitchers, formed by the complete union of the margins, and falling off by a transverse fissure (as in the calyx of Escholtzia).

 Tulipa Gesneriana.

B. Polyphyllous.

1. Diphyllous, formed by the union of two leaves into a single cup, tube, or funnel, &c.

 Pisum sativum (stipules)!

 Crassula arborescens.

 Polygonatum multiflorum.

2. Triphyllous, formed by the union of three leaves.

 Paris quadrifolia var.

Besides the above varieties of ascidia formed from the union of one or more leaves, there are others which seem to be the result of a peculiar excrescence or hypertrophy of the leaf. Such are some of the curious pitcher-like structures met with occasionally in the leaves of cabbages, lettuces, Aristolochia, &c. See Hypertrophy, cup-like deformities, &c.

In addition to other publications previously mentioned, reference may be made to the following treatises on the subject of ascidia:—Bonnet, 'Rech. Us. Feuilles,' p. 216, tab. xxvi, f. 1, Brassica; De Candolle, 'Trans. Hort. Soc.,' t. v, pl. 1, Brassica; Id., 'Org. Veget.,' I, 316; 'Bull. Soc. Bot. Fr.,' I, p. 62, Polygonatum; 'Bull. Acad. Belg.,' 1851, p. 591, Rosa; Hoffmann, 'Tijdschrift v. Natuur. Geschied.,' vol. viii, p. 318, tab. 9, Ceratonia; C. Mulder, 'Tijdschrift, &c.,' vol. vi, p. 106, tab. 5, 6, Trifolium, Mimosa, Staphylea;' Molkenboer,' p. 115, t. 4, Brassica.