CHAPTER II.

ADHESION.

Adhesion, so called, occurs either from actual union of originally distinct members of different whorls or from the non-occurrence of that separation which usually takes place between them. It is thus in some degree a graver deviation than cohesion, and is generally a consequence of, or at least is coexistent with, more serious changes; thus if two leaves of the same whorl are coherent the change is not very great, but if two leaves belonging to different whorls, or two leaves in the same spiral cycle are adherent, a deformation in the axis or a certain amount of dislocation must almost necessarily exist. Adhesion as a normal occurrence is usually the result of a lack of separation rather than of union of parts primitively separate. Instances of adhesion between different organs is seen under ordinary circumstances in the bract of the Lime tree, which adheres to the peduncle, also in _Neuropeltis_, while in _Erythrochiton hypophyllanthus_ the cymose peduncles are adherent to the under surface of the leaf.

Adhesion between the axes of the same plant is sufficiently treated of under the head of Cohesion, from which it is in this instance impossible to make a distinction. Adhesion of the inflorescence is necessarily a frequent accompaniment of fasciation and cohesion of the branches.

=Adhesion of foliar organs= may occur either between the margins or between the surfaces of the affected parts; in the former case there is almost necessarily more or less displacement and change of direction, such as a twisting of the stem and a vertical rather than a horizontal attachment of the foliar organ to it; hence it generally forms but a part of other and more important deviations.

=Adhesion of leaves by their surfaces.=--The union of leaves by their surfaces is not of very frequent occurrence, many of the instances cited being truly referable to other conditions. Bonnet describes the union of two lettuce leaves, and Turpin that of two leaves of _Agave americana_, in which latter the upper surface of one leaf was adherent to the lower surface of the leaf next above it, and I have myself met with similar instances in the wallflower and in lettuce and cabbage leaves; other instances have been mentioned in _Saxifraga_, _Gesnera_, _&c._[30]

In these cases, owing to the non-development of the internodes, the nascent leaves are closely packed, and the conditions for adhesion are favorable, but in most of the so-called cases of adhesion of leaf to leaf by the surface, a preferable explanation is afforded either by an exuberant development (hypertrophy) or by chorisis (see sections on those subjects). Thus, when a leaf of this kind is apparently so united, that the lower surface of one is adherent to the corresponding surface of another, the phenomenon is probably due rather to extra development or to fission. There is an exception to this, however, in the case of two vertically-erect leaves on opposite sides of the stem; here the two upper or inner surfaces may become adherent, as in an orange, where two leaves were thus united, the terminal bud between them being suppressed or abortive.

Adhesion between the membranous bract of _Narcissus poeticus_ and the upper surface of the leaf is described by Moquin.[31] The same author mentions having seen a remarkable example of adhesion in the involucels of _Caucalis leptophylla_, the bracts of which were soldered to the outer surface of the flowers. M. Bureau[32] mentions an instance wherein the spathe of _Narcissus biflorus_ was partially twisted in such a manner that the lower surface of its median nerve was adherent to the corresponding surface of one of the sepals, mid-rib to mid-rib, thus apparently confirming a law of G. de Hilaire, that when two parts of the same individual unite, they generally do so by the corresponding surfaces or edges, but the rule is probably not so general in its application as has been supposed.

=Adhesion of foliar to axile organs.=--The appendicular organs may likewise be found united to the axile ones. This union takes place in many ways; sometimes the leaves do not become detached from the stem for a considerable distance, as in the so-called decurrent leaves, at other times the leaves are prolonged at their base into lobes, which are directed along the stem, and are united with it. Turpin records a tendril of a vine which was fused with the stem for some distance, and bore leaves and other tendrils. Union of the leaf or bract with the flower-stalk is not uncommon. It occurs normally in the Lime and other plants.

=Adhesion of the sepals to the petals= is spoken of by Morren as calyphyomy, [Greek: kalyx phyomai.][33] Moquin cites an instance in _Geranium nodosum_, in which one petal was united by its lower surface to one of the segments of the calyx. A similar circumstance has been observed in _Petunia violacea_ by Morren. Duchartre describes an instance wherein one of the outer sepals of _Cattleya Forbesii_ was adherent to the labellum.[34]

=Adhesion of the stamens to the petals= is of common occurrence under natural circumstances. Cassini has described a malformation of _Centaurea collina_, in which two of the five stamens were completely grafted with the corolla, the three others remaining perfectly free. Adhesion of the petals to the column is not of infrequent occurrence among Orchids. I have observed cases of the adhesion of the segments of the perianth to the stamen in _Ophrys aranifera_, _Odontoglossum_, _sp_. &c. It is the ordinary condition in _Gongora_ and some other genera. I have seen it also in _Lilium lancifolium_. Some forms of _Crocus_, occasionally met with, present a very singular appearance, owing to the adhesion of the stamens to the outer segments of the perianth, the former, moreover, being partially petaloid in aspect. M. de la Vaud[35] speaks of a similar union in _Tigridia pavonia_. Morren[36] describes a malformation of _Fuchsia_ wherein the petals were so completely adherent to the stamens, that the former were dragged out of their ordinary position, so as to become opposite to the sepals; the fusion was here so complete that, no trace of it could be seen externally. It should be remarked that it was the outer series of stamens that were thus fused.[37]

=Adhesion of stamens to pistils.=--The stamens also may be united to the pistils, as in gynandrous plants. Moquin speaks of such a case in a _Scabious_; M. Clos in _Verbascum australe_.[38] I have seen cases of the same kind in the Wallflower, Cowslip (_Primula veris_), Tulip, Orange, in the garden Azalea and other plants.

=Miscellaneous adhesions.=--Sometimes organs, comparatively speaking, widely separated one from the other, become united together. Miquel has recorded the union of a stigma with the middle lobe of the lower lip of the corolla of _Salvia pratensis_.[39] In the accompanying figure [fig. 13], taken from a double wallflower, there is shown an adhesion between a petal and an open carpel on the one side, and a stamen on the other.

Moquin speaks of some pears, which were united, at an early stage, with one or two small leaves borne by the peduncle and grafted to the fruit by the whole of their upper surface. As the pear increased in size the leaves became detached from it, leaving on the surface of the fruit an impression of the same form as the leaf, and differing in colour from the rest of the surface of the fruit. Traces of the principal nerves were seen on the pear.

It is curious to notice how very rare it is for the calyx to adhere to the ovary in flowers where that organ is normally superior. The "_calyx inferus_" seems scarcely ever to become "_calyx superus_," while, on the other hand, the "_calyx normaliter superus_" frequently becomes inferior from detachment from, or from want of union with the surface of the ovary.

=Adhesion of fruit to branch.=--Of this Mr. Berkeley[40] cites an instance in a vegetable marrow (_Cucumis_), where a female flower had become confluent with the branch, at whose base it was placed, and also with two or more flowers at the upper part of the same branch, so as to make an oblique scar running down from the apex of the fruit to the branch.

=Synanthy.=--Adhesion of two or more flowers takes place in various ways; sometimes merely the stalks are united together, so that we have a single peduncle, bearing at its extremity two flowers placed in approximation very slightly adherent one to the other. In this manner I have seen three flowers of the vegetable marrow on a common stalk, the flowers themselves being only united at the extreme base. Occasionally cases may be met with wherein the pedicels of a stalked flower become adherent to the side of a sessile flower. I have noticed this commonly in _Umbelliferæ_. Union of this kind occurs frequently in the common cornel (_Cornus_), wherein one of the lower flowers becomes adherent to one of the upper ones. In De Candolle's 'Organographie Végétale,' Plates 14 and 15, are figured cases of fusion of the flower stems of the Hyacinth and of a _Centaurea_. In other cases the union involves not only the stalk but the flowers themselves; thus fusion of the flowers is a common accompaniment of fasciation, as was the case in the _Campanula_ figured in the cut (fig. 14).

Synanthy may take place without much derangement of the structure of either flower, or the union may be attended with abortion or suppression of some of the parts of one or both flowers. Occasionally this union is carried to such an extent that a bloom appears to be single, when it is, in reality, composed of two or more, the parts of which have become not only fused, but, as it were, thrust into and completely incorporated one with another, and in such a manner as to occupy the place of some parts of the flower which have been suppressed. It must not be overlooked that this adhesion of one flower to another is a very common occurrence under natural circumstances, as in _Lonicera_, in the common tomato, in _Pomax_, _Opercularia_, _Symphyomyrtus_, &c., while the large size of some of the cultivated sunflowers is in like manner due to the union of two or more flower-heads.

One of the simplest instances of synanthy is that mentioned by M. Duchartre,[41] in which two flowers of a hyacinth were united together simply by means of two segments of the perianth one from each flower. A similar occurrence has been cited by M. Gay in _Narcissus chrysanthus_. In like manner the blossoms of Fuchsias or Loniceras occasionally become adherent merely by their surface, without involving any other change in the conformation of the flowers. M. Maugin alludes to a case of this kind in _Aristolochia Clematitis_.[42]

But it is more usual for some of the organs to be suppressed, so that the number of existing parts is less than would be the case in two or more uncombined flowers. A few illustrations will exemplify this. In two flowers of _Matthiola incana_, that I observed to be joined together, there were eight sepals, eight petals, and ten perfect stamens, eight long and two short, instead of twelve. Closer examination showed that the point of union between the two flowers occurred just where, under ordinary circumstances, the two short stamens would be. In this instance but little suppression had occurred. In similar flowers of _Narcissus incomparabilis_ I remarked a ten-parted perianth, ten stamens within a single cup, two styles, and a five-celled ovary. Here, then, it would appear that two segments of the perianth, two stamens, and one carpel were suppressed. In a Polyanthus there were nine sepals, nine petals, nine stamens, and a double ovary.

As an illustration of a more complicated nature reference may be made to three flowers of _Aconitum Napellus_, figured by A. de Chamisso, 'Linnæa,' vol. vii, 1832, p. 205, tab. vii, figs. 1, 2. In this specimen the two outer blossoms had each four sepals present, namely, the upper hooded one, one of the lateral sepals, and both of the inferior ones; the central flower had only the upper sepal and one other, probably one of the lower sepals; thus there were but ten sepals instead of fifteen. The nectary-like petals, the stamens, and pistils were all present in the lateral flowers, but were completely suppressed in the middle one. A less degree of suppression was exemplified in a triple flower of _Calanthe vestita_ sent me by Dr. Moore, of Glasnevin, in which all the parts usually existing in three separate flowers were to be found, with the exception of the spur belonging to the labellum of the middle flower (figs. 15, 16).

One of the most common malformations in the Foxglove (_Digitalis_) results from the fusion of several of the terminal flowers into one. In these cases the number of parts is very variable in different instances; the sepals are more or less blended together, and the corollas as well as the stamens are usually free and distinct, the latter often of equal length, so that the blossom, although truly complex, is, as to its external form, less irregular than under natural circumstances. The centre of these flowers is occupied by a two to five-celled pistil, between the carpels of which, not unfrequently, the stem of the plant projects, bearing on its sides bracts and rudimentary flowers. (See Prolification.) An instance of this nature is figured in the 'Gardeners' Chronicle,' 1850, p. 435, from which the cut (fig. 17) is borrowed.

One of the most singular recorded instances of changes connected with fusion of the flowers is that cited by Reinsch,[43] where two female flowers of _Salix cinerea_ were so united with a male one as to produce an hermaphrodite blossom.

It follows, from what has been said, that the number of parts that are met with in these fused flowers varies according to the number of blossoms and of the organs which have been suppressed. Comparatively rarely do we find all the organs present; but when two flowers are united together we find every possible variety between the number of parts naturally belonging to the two flowers and that belonging to a single one. Sometimes instances are met with wherein the calyx does not present the normal number of parts, while the other parts of the flower are in excess. I have seen in a _Calceolaria_ a single calyx, with the ordinary number of sepals, enclosing two corollas, adherent simply by their upper lips, and containing stamens and pistils in the usual way. In this instance, then, the sepals of one flower must have been suppressed, while no such suppression took place in the other parts of the flower.

Professor Charles Morren paid special attention to the various methods in which the flowers of Calceolarias may become fused, and to the complications that ensue from the suppression of some parts, the complete amalgamation of others, &c. Referring the reader to the Belgian savant's papers for the full details of the changes observed, it is only necessary to allude to a few of the most salient features.

Sometimes the upper lips of two flowers are fused into one, the two lower remaining distinct. In other cases, the upper lip disappears altogether, while there are two lower lips placed opposite one another;, of the stamens, sometimes the outermost, at other times the innermost disappear.[44]

Occasionally there appears to be, as it were, a transference of the parts of one flower to another. One of the simplest and most intelligible cases of this kind is recorded by Wigand in the 'Flora' for 1856, in a compound flower of _Polygonatum anceps_, in which within a twelve-parted perianth there were twelve stamens and two pistils, one four-celled, the other two-celled; hence it would appear as if a carpel belonging to one flower had become united to those constituting the pistil of the adjacent one. Among Orchids this fusion of some of the elements of different flowers, together with the suppression of others, is carried to such an extent as to render the real structure difficult to decipher. Sometimes flowers of _Ophrys aranifera_, at first sight seeming normal as to the number, and almost so as regards the arrangement of their parts, have yet, on examination, proved to be the result of a confluence of two flowers. Mr. Moggridge has observed similar phenomena in the same species at Mentone.

Sometimes the fusion affects flowers belonging to different branches of the same inflorescence, as in _Centranthus ruber_, described by Buchenau, 'Flora,' 1857, p. 293, and even a blossom of one generation of axes may be united with a flower belonging to another generation. Thus M. Michalet[45] speaks of a case wherein the terminal flower of _Betonica alopecuros_ was affected with Peloria, and fused with an adjacent one belonging to a secondary axis of inflorescence, and not yet expanded. This latter flower had no calyx, but in its place were three bracts, surrounding the corolla; this again was united to the calyx of the terminal bloom in a most singular manner, the limb of the corolla and that of the calyx being so joined one to the other as to form but a single tube. It is not uncommon, as has been before stated, to find two corollas enclosed within one calyx, but this is probably the only recorded instance of the fusion of the calyx and corolla of two different flowers belonging to two different axes.

From the preceding details, as well as from others which it is not necessary to give in this place, it would appear that synanthy is more liable to occur where the flowers are naturally crowded together[46] than where they are remote; so too, the upper or younger portions of the inflorescence are those most subject to this change. In like manner the derangements consequent on the coalescence of flowers are often more grave in the central organs, which are most exposed to pressure, and have the least opportunities of resisting the effects of that agency, than they are in the outer portions of the flowers where growth is less restricted.

Morren in his papers on synanthic _Calceolarias_, before referred to, considers that the direction in which fusion acts is centripetal, _e.g._ from the circumference towards the centre of the flower, thus reversing the natural order of things. He considers that there is a radical antagonism between the normal organizing forces and the teratological disorganizing forces, and explains in this way the frequent sterility of monsters from an imperfect formation of stamens, or pistils, or both.

The greater tendency in synanthic flowers of parts of one whorl to adhere to the corresponding organs in another flower has often been remarked, though the dislocation of parts may be so great as to prevent this from being carried out in all cases. It appears also that synanthy is more frequently met with among flowers which have an inferior ovary than in those in which the relative position of the organ in question is reversed. This remark applies particularly to individual cases; the proportion as regards the genera may not be so large. The explanation of this must of course depend on the circumstances of each particular case; and it would be wrong to attempt to lay down a general rule, when organogenists have not yet fully decided in what plants the inferior ovary is an axial structure, and in what others the appearance is due to the adhesion of the base of the calyx to the carpels.

The list which follows is not intended as a complete one, but it may serve to show what plants are more particularly subject to this anomaly; the * indicates unusual frequency of occurrence, the ! signifies that the writer has himself seen instances in the plants named. Many of the recorded cases of Synanthy are really cases of adhesion of the inflorescence rather than of the flowers.

Ranunculus Lingua. bulbosus! Aconitum Napellus. Delphinium sp.! Matthiola incana! Arabis sagittata. Silene sp. Reseda odorata! Vitis vinifera. Citrus aurantium. *Fuchsia var. hort.! OEnothera sp. Saxifraga sp. Podalyria myrtillifolia. Prunus Armeniaca. spinosa. Pyrus Malus. Persica vulgaris. Cratægus monogyna. Robinia pseudacacia. Gleditschia triacanthos. Syringa persica. Cornus sanguinea. Viburnum sp. *Lonicera sp. plur! Centranthus ruber! Valantia cruciata. Centaurea moschata. Jacea. Zinnia elegans. Zinnia revoluta. Helianthus sp.! Spilanthes oleracea. Dahlia. *Leontodon Taraxacum! Senecio Doria. Cichorium Intybus. Lactuca sativa. Anthemis retusa. *Campanula medium! persicifolia. Azalea indica! Vinca minor. Atropa Belladonna. *Solanum Lycopersicum! *Petunia violacea! Galeopsis ochroleuca. Betonica alopecuros. *Digitalis purpurea! *Antirrhinum majus! *Linaria purpurea! *Pedicularis sylvatica! *Calceolaria var. hort.! Scrophularia nodosa. Salpiglossis straminea. Streptocarpus Rexii. *Gesnera var. hort.! Æschynanthus sp.! Thyrsacanthus rutilans! Anagallis collina. *Primula veris! Auricula. *Primula acaulis, var. umbellata! elatior? * sinensis! Aristolochia Clematitis. Blitum sp. Chenopodium sp. Rumex sp. Salix cinerea. *Hyacinthus orientalis! Lilium bulbiferum! croceum, et sp. alix, pl. Tulipa, sp. Polygonatum anceps. Fritillaria imperalis! Agave americana. Iris versicolor. sambucina. Crocus, sp. Colchicum autumnale. Narcissus incomparabilis! Tazetta. biflorus. chrysanthus. *Ophrys aranifera! Calanthe vestita! Oncidium bicolor. ornithorhyncum. &c. &c.

In addition to the works before cited, additional information on this subject may be gained from the following:--Jaeger, 'Missbilld.,' p. 92. v. Schlechtend, 'Bot. Zeit.,' 1856, _Robinia_. Weber, 'Verhandl. Nat. Hist. Vereins. Preuss. Rheinl.,' 1849, p. 290, _Primula_. Hincks, 'Rep. Brit. Assoc. Newcastle,' 1838, _Salpiglossis_. Clos, 'Mém. Acad. Toulouse,' vol. vi, 1862, _Anagallis_. Wigand, 'Flora,' 1856, tab. 8, _Pedicularis_. Henfrey, 'Botan. Gazette,' i, p. 280, _Reseda_. P. Reinsch, 'Flora,' 1860, tab. 7, _Petasites_. Weber, Verhandl. Nat. Hist. Vereins. f.d. Preuss. Rheinl. u. Westphal.,' 1860, p. 332, tabs. 6 et 7, _Prunus_, _Persica_, _Campanula_, _Taraxacum_, _Saxifraga_, _Silene_, _Hyacinthus_, _&c._ Miquel, 'Linnæa,' xi, p. 423, _Colchicum_. Michel, 'Traité du Citronnier,' tab. 6, _Citrus_.

=Syncarpy.=--In the preceding section it has been shown that the carpels, like other parts of the flower, are subject to be united together. This union may either take place between the carpels of a single flower or between the pistils of different flowers. In the latter case the other floral whorls are generally more or less altered. Where, however, the ovary is, as it is called, inferior, it may happen that the pistils of different flowers may coalesce more or less without much alteration in the other parts of the flower, as happens normally in many _Caprifoliaceæ_, _Rubiaceæ_, &c. &c. In some of these cases it must be remembered that the real structure of the apparent fruit is not made out beyond dispute, the main points of controversy being as to what, if any, share the dilated fruit-stalk or axis takes in the formation of such organs. Again, it will be borne in mind that in some cases the so-called fruit is made up of a number of flowers all fused together, as in the Mulberry or the Pineapple, in which plants what is, in ordinary language, called the fruit really consists of the whole mass of flowers constituting the inflorescence fused together. Union of the fruits may also in some cases take place between the carpels after the fall of the other floral whorls, particularly when the outer layers of the pericarp assume a succulent condition, so that under the general head of syncarpy really different conditions are almost necessarily grouped together, and, in seeking to investigate the causes of the phenomenon, the particular circumstances of each individual case must be taken into account. Syncarpy takes place in various degrees; sometimes only the stalks are joined; at other times the whole extent of the fruit, as in cherries, &c. This peculiarity did not escape the observant mind of Shakespeare--

"A double cherry seeming parted. But yet a union in partition, Two lovely berries moulded on one stem." 'Midsummer Night's Dream,' act iii, sc. 2.

A similar union has been observed in peaches, gooseberries, gourds, melons, and a great many other fruits. In the Barbarossa grape I have frequently seen a fusion of two, three, four or more berries quite at the end of the bunch, so that the clusters were terminated by a compound grape. Seringe has remarked sometimes two, sometimes three, fruits of _Ranunculus tripartitus_ soldered together. He has also seen three melons similarly joined.[47] Turpin mentions having seen a complete union between the three smooth and leathery pericarps which are naturally separate and enclosed within the spiny cupule of the chestnut.[48] Poiteau and Turpin have figured and described in their treatise on fruit trees, under the name of Néfle de Correa, four or five medlars, joined together and surmounted by all the persistent leaflets of the calyces.[49]

A very remarkable example of Syncarpy has been recorded by E. Koenig in which nine strawberries were borne on one stem (_Fragaria botryformis_),[50] and a similar malformation has been observed in the Pineapple.

When two fruits are united together they may be of about equal size, while in other cases one of the two is much smaller than the other. This was the case in two cucumbers given to me by Mr. James Salter. These were united together along their whole length excepting at the very tips; the upper one of the two was much larger than the lower, and contained three cells, the lower fruit was one-celled by suppression. Both fruits were curved, the curvature being evidently due to the more rapid growth of the upper as compared with the lower one.

In many of these cases, where the fruits are united by their bases, the summits become separated one from the other, so as to resemble the