Loudon's encyclopædia of plants : comprising the specific character, description, culture, history, application in the arts, and every other desirable particular respecting all the plants indigenous to, cultivated in, or introduced to Britain / [J.C. Loudon].

  • Loudon, J. C. (John Claudius), 1783-1843.
Date:
1855
Catalogue details

Licence: Public Domain Mark

Credit: Loudon's encyclopædia of plants : comprising the specific character, description, culture, history, application in the arts, and every other desirable particular respecting all the plants indigenous to, cultivated in, or introduced to Britain / [J.C. Loudon]. Source: Wellcome Collection.

    690/1618 (page 660)
    Class XIX.—SYNGENESIA. Stamens 5. Anthers united by their edges. Tma is one of the most extensive and best defined of all the Linnean classes. Its essential character depends, as its name indicates, (oro, together, and yivm;, generation,) upon the adhesion of the anthera; or male organs of the flower into a single tube. It comprehends the whole of the Corymb?ferae, Cichoracea?, and Cinaroce- phalee of Jussieu; and, with the exception of Aciearpheae, nothing else. The genera constituting the order Monogainia of Linnaeus are excluded by Linnean botanists of the present day. In addition to the cohesion of the anthers, upon which this class immediately depends, it is further charac- terized by the flowers, commonly called florets, being clustered together in heads, and inserted upon a common receptacle, which is surrounded by an involucrum, commonly, but very improperly, termed calyx. The few genera, such as Kuhnia, Euxenia, Acicarpha, &c., in which a union of anthers either does not exist at all, or in a very incomplete degree, are therefore retained in Syngenesia, because of their congruity in the structure of their inflorescence. The real nature of the various constituent parts of syngenesious inflorescence being, from its complicated nature, very puzzling to the unlearned, and, as it would seem, to some professors also, it may be useful to ex- plain briefly the analogy the various parts bear to the organs of other plants, and the terms employed in de- scribing them. The Head or Capitulum is a cluster of flowers of the nature of an umbel, inserted upon a common rachis, which, by contraction or incomplete developement, assumes the form of a conical or flat body, out of which the flowers proceed, and which is called a receptacle. This is surrounded by the involucrum. M. Cassini calls the head Calathide. The Involucrum is the most external part of the head. It consists of a more or less considerable number of scales or leaves, placed in a single row, either distinctly from each other, or united at their edges, in which case the involucrum is called one-leaved ; or placed in many rows, becoming gradually shorter as they are ex- ternal, in which case they are called imbricated. If the external scales surround the internal at the base in a regular manner, then the involucrum is said to be calyeulate. The involucrum was called common calyx by Linnaeus, and has been more recently denominated a perianthium. M. Cassini names it Periclinium. The Receptacle (Clmanthium of Cassini) is a cellular fungous surface surrounded by the involucrum, and bearing the florets. It is either columnar, conical, flat, or depressed ; and naked, or covered with appendages called hairs or bristles, according to their nature, or palea?, when they are dilated and have a glumaceous ap- pearance. If naked, and merely scarred by the insertions of the florets, it is called dotted or puncticulale ; when the scars are more considerable and deeper, the receptacle is said to be scrobiculate; if the insertions are so deep as to appear to be divided by membranous partitions, it is cellular, or favose, or alveolate; if fur- nished with hairs, it is villose ; if with palea?, it is paleaceous or chaffy. The Falae are of the same nature as bractea?, and exist in various degrees of developement. Occasionally they are as large as the scales of the involuorum, which they in that case closely resemble. The flower, usually termed Floret, consists of two parts, the ovarium and the corolla, each with its appen- dages. The Ovarium is always one-celled, but it occasionally has two additional obsolete cells, as in Arctotis. It is either naked, or covered with hairs in various degrees, occasionally becoming enveloped in fine wool, and it is surmounted by an organ named the pappus. The Pappus has generally been esteemed a superior calyx, and it is the opinion cf M. Cassini that it is analo- gous to the scales of the receptacle, and the leaves of the involucrum. The Corolla is placed on the top of the ovarium. It is either funnel-shaped, with a limb divided into four or five equal lobes, in which case the florets are denominated tubular ; or it is split on one side, and spread open into the form of a strap, when the florets are called ligulate ; or it is divided into two portions, of which one is unequal to the other ; this form is called bilabiate or two-lipped. Bilabiate corollas may be either ligulate cr flosculous, according to the species to which they belong. Occasionally the corolla appears to he absent. The Stamens are attached to the orifice of the tube of the corolla, just below the limb. Their filaments are usually, but not always, distinct; their anthers are adherent by their edges, and furnished with a little mem- branous appendage at the tip, and sometimes with two spur-like processes at their base. The Style is filiform, and either split at the summit into two linear spreading stigmas, or consists of a single piece from the base to the summit. The form and surface of the stigma, and the upper part of the style are subject to a great diversity of appearances, which are of the utmost importance in determining the affinities of the genera. The Florets are either hermaphrodite, unisexual, or neuter. Upon these differences of sex the orders of Lin- naeus are founded. In Syngenesia aqualis the florets are all hermaphrodites. In Syngenesia superflua, those of the disk or centre are hermaphrodite, of the circumference or ray female, (and superfluous.) In Syngenesia frustranea, those of the disk are hermaphrodite, of the ray neuter, (and useless.) In Syngenesia necessaria, those of the disk are male, of the ray female, (and necessary.) Syngenesia segregata is only characterized by the heads themselves being clustered and surrounded by a com- mon involucrum. The genera of Syngenesia have always attracted much attention from systematic botanists, who have met with very unequal success in characterizing them. The older botanists comprised them all under a few general heads or names. Tournefort, with his usual happiness, pointed out a large proportion of the most natural ge- nera. Vaillant established a considerable number. Linnaeus, profiting by the labours of his predecessors, re- jecting some genera, and dividing others, increased their number, and adapted them to his sexual system, in nearly the same order in which they exist at the present day. Jussieu, by applying to the genera the princi- ples of his natural method, reduced them to an arrangement much superior in point both of facility and of natural affinity to that of his northern rival. But however meritorious the labours of these great systematists may have been, much remained to be effected, even among their own plants, by those who followed them. The indefatigable Gartner, who worked upon the only satisfactory or philosophical principle, that of strict analysis, soon discovered that the combinations of Linnaeus and Jussieu were often too vague and ill defined to accord with his notions of accurate subdivision. Hence many other genera arose. But since his days, the extent of Syngenesia has, like all other parts of botanical science, increased exceedingly, and has arrived in our days at a state little short of absolute confusion. Injudicious or superficial botanists, impressed with the fear of inno- vation, and with a pious reverence even for the errors of those who went before them, have from time to time crowded the genera of Jussieu and Linnaeus with the most incongruous species, and so have rendered many of those which were originally pure and simple, heterogeneous masses of species. Much has been done by oui learned countryman, Mr. Robert Brown, to reduce to order this class of individuals, and, as far as his published observations have extended, with the happiest success. In France, an ingenious and accurate observer, Mr. Henry Cassini, lias undertaken a revision of the whole class, upon principles peculiar to himself; and it must be allowed, that what he has executed has given ample room for regret that he has not published more. Un- fortunately, his observations are scattered over the face of many books, and are in no case in such a state of arrangement as to be extensively useful. It is hoped that a period will soon arrive when he, or at least some