ORDER XXVIII. RAFFLESIACEE.-RAFFLESIADS.

Rafflesiacere, Endlicher Meletemata, p. 14. (1832); Gen. xli. Meisner, p. 367; R. Brown in Linn. Trans. 19. 241.

DIAGNOSIS. Stemless and stalkless; flowers 5-parted, sessile on the branches of trees, solitary, with anthers opening by pores, and innumerable ovules growing over parietal placenta.

Stemless plants, consisting merely of flowers growing immediately from the surface of branches, and immersed among scales; flowers hermaphrodite, or dioecious. Perianth

Fig. LXVIll.

superior, globose or campanulate; the limb 5-parted, with the segments imbricated or doubled inwards in æstivation; the throat surrounded by calli, which are either distinct 1 or run together into an entire ring. Column (synema) hypocrateriform or sub-globose, adhering to the tube of the perianth; anthers numerous, distinct, or somewhat connate, adhering by the base, in one row; 2-celled, with the cells opposite, and each opening by a vertical aperture, or concentrically many-celled with a common pore. Ovary inferior, 1-celled, with many-seeded parietal placentæ; styles conical, equal in number to the placentæ, run together within the column, but pro3 jecting beyond it, and then distinct. Fruit, an indehiscent pericarp, with an infinite multitude of seeds. [Embryo undivided, with or without albumen.-R. Brown.]

These extraordinary plants have no stems whatever, but consist of flowers only, supported by scales in room of leaves. Among them is the very remarkable species described by Brown in the 13th vol. of the Linnean Society's Transactions, under the name of Rafflesia, to which those may be referred who are desirous either of knowing what is the structure of one of the most anomalous of vegetables, or of finding a model of botanical investigation and sagacity, or of consulting one of the most beautiful specimens of botanical analysis which Francis Bauer ever made. They differ from the Cistusrapes in having no proper stem, in their anthers being porous, and in their flower, which constitutes the whole plant, being divided by 5, like Exogens, instead of 2 or 3, like Endogens. An affinity has been suggested with Birthworts, to which this Order seems to have no immediate relationship.

Natives of the East Indies, on the stems of Cissi; or of South America, on the branches of leguminous plants.

Rafflesia Patma is employed in Java as a powerful styptic, in relaxation or debility of the urino-genital apparatus, and Brugmansia seems to possess similar qualities.

GENERA.

Brugmansia, Blume. **A PODANTHEE, R. Br. | Pilostyles, Guillem.

Zippelia, Rchb.

Apodanthes, Poit.

Mycetanthe, Rchb.

NUMBERS. GEN. 5. Sp. 16.

Aristolochiacea?

Frostia, Bert.

POSITION.-Balanophoraceae-RAFFLESIACEE.-Cytinacea.

Fig. LXVIII-Pilostyles Berterii 3 1. A vertical section of a flower; 2. a young flower bursting through the bark; 3. a head of stamens.

MYSTROPETALINÆ.-J. D. Hooker.

"A genus of monoecious root-parasites. Stem sheathing, covered with imbricating scales, terminated by a dense-flowered head. Flowers with three villous bracteæ. Males on upper part of the spike; of three valvate sepals connate at the base. Stamens two, inserted on the petals and opposite them; anthers posticous; pollen angular. Female flower; perianth superior, tubular, 3-toothed, minute; ovary 1-celled, with one pendulous ovule, seated on a disc; style filiform; stigma 3-lobed. Fruit a spherical achene, 1-celled, with one albuminous seed filling the cavity; structure as in Balanophoreæ.

"Mystropetalum is well described by Griffith (note in Linnean Transactions, vol. xix. p. 336), who, however, strangely overlooked the pendulous ovule and the embryo, which, though small, is very evident, broad, has a short blunt radicle pointing upwards, and two short broad cotyledons, just as in Gunnera. The testa is a very thin membrane. Albumen of very large hard grains. The genus appears near Loranthaceæ in many respects, and betrays some affinity with Composite. It is another, in short, of the many incomplete epigynous orders, such as Loranthaceæ, Santalacea, Corneæ, Araliacea, Balanophoreæ, Gunneraceæ, Halorageæ, &c. &c., which are all obscure, often imperfect as to floral envelopes and ovules, and of very difficult and uncertain affinity."

ONLY GENUS.
Mystropetalon, Harvey.

Two species only are known, both natives of S. Africa.

J. D. HOOKER.

CLASS IV.-ENDOGENS.

Monocotyledones, Juss. Gen. 21. (1789); Desf. Mém. Inst. 1. 478. (1796). Endorhizeæ, Rich. Anal. (1808). Monocotyledoneæ or Endogenæ, DC. Théorie, 207. (1813). Meisner, p. 353. Cryptocotyledoneæ or Graniferæ, Agardh. 73. (1821).-—Amphibrya, Endl. Gen. p. 76.-Teleophyta, Schleiden. Having now passed in review the absolutely sexless plants, called Thallogens, and all that class which, under the title of Acrogens, comprehends a numerous race among whom the existence of a double sex is conjectured to exist, and having, moreover, disposed of the curious Rhizogens, which, to a fungal mode of growth join a complete sexual apparatus, we pass to Endogens, or Monocotyledons.

Here we find a vast multitude of species, with extremely diversified habits, among whom occurs every attribute supposed to be connected with the most perfect structure. Leaves and stems are distinctly separated; spiral vessels, breathing-pores, and sexes, are in a condition that admits of no further complication; and we find in the great majority everything which constitutes as elaborate an arrangement of parts as we have any knowledge of in the vegetable kingdom.

This great class bears the name of Endogens, in consequence of its new woody matter being constantly developed in the first instance towards the interior of the trunk, only curving outwards in its course downwards. That palm-trees grow in this way was known so long since as the time of Theophrastus, who distinctly speaks of the differences between endogenous and exogenous wood.* But that this peculiarity is also extended to a considerable part of the vegetable kingdom is a modern fact, the discovery of which we owe to the French naturalists Daubenton and Desfontaines. The path being thus opened, the inquiry has subsequently, and more particularly of late years, been much extended, and the result is the conviction that all those numerous races to which Jussieu applied the name of Monocotyledoneæ, agree essentially in this manner of growth. We may take the palm-tree as typical of the endogenous structure. In the beginning the embryo of a palin consists of a cellular mass of a cylindrical form, very small and not at all divided. As soon as germination commences a certain number of cords of ligneous fibre begin to appear in the radicle, deriving their origin from the plumule. Shortly afterwards, as soon as the rudimentary leaves of the plumule begin to lengthen, spiral and dotted vessels appear in the tissue in connection with the ligneous cords; the latter increase in quantity as the plant advances in growth, shooting through the cellular tissue, and keeping parallel with the outside of the root. At the same time the cellular tissue increases in diameter to make room for the ligneous cords (or woody bundles, as they are also called). At last a young leaf is developed with a considerable number of such cords in connection with its base, and, as its base passes all round the plumule, these cords are consequently connected equally with the centre which that base surrounds. Within this a second leaf gradually unfolds, the cellular tissue increasing horizontally at the same time; the ligneous cords, however, soon cease to maintain anything like a parallel

* Εχει δὲ τὴν μήτραν, τὰ μὲν μεγάλην καὶ φανερὰν, ὡς Πρίνος, Δρύς, καὶ τὰ ἄλλα τὰ προειρημένα· τὰ δὲ, ἀφανιστήκαν, διον, Ελαία, Πύξος· οὐ γὰρ ἐστιν ἀφορισμένην οὕτω λαβεῖν· ἀλλὰ καὶ φασί τινες οὐ κατὰ τὸ μέσον, άλλα κατὰ τὸ πᾶν ἔχειν, ὥστε μὴ εἶναι τότον ὡρισμένον· διὸ καὶ ἔνια οὐ δ ̓ ἂν δόξειεν ὅλως ἔχειν· ἐπεὶ καὶ τοῦ Τούμπου ουδεμία φαίνεται διαφορὰ κατ' ουδέν. Theophr. Hist. I. 8.

direction, but form arcs whose extremities pass upwards and downwards, losing their extremities in the leaf on the one hand, and on the other in the roots, or in the cellular integument on the outside of the first circle of cords; at the same time the second leaf pushes the first leaf a little from the centre towards the circumference of the cone of growth. In this manner leaf after leaf is developed, the horizontal cellular system enlarging all the time, and every successive leaf, as it forms at the growing point, emitting more woody bundles curving downwards and outwards, and consequently intersecting the older arcs at some place or other; the result of which is that the first formed leaf will have the upper end of the arcs which belong to it longest and much stretched outwardly, while the youngest will have the arcs the straightest; and the appearance produced in the stem will be that of a confused entanglement of woody bundles in the midst of a quantity of cellular tissue. As the stem extends its cellular tissue longitudinally while this is going on, the woody arcs are consequently in proportion long, and in fact usually appear to the eye as if almost parallel, excepting here and there, where two arcs intersect each other. As in all cases the greater number of arcs curve outwards as they descend, and eventually break up their ends into a multitude of fine divisions next the circumference where they assist in forming a cortical integument, it will follow that the greater part of the woody matter of the stem will be collected near the circumference, while the centre, which is comparatively open, will consist chiefly of cellular tissue; and when, as in many palms, the stem has a limited circumference, beyond which it is its specific nature not to distend, the density of the circumference must, it is obvious, be proportionably augmented. It is however a mistake to suppose that the great hardness of the circumference of old palm wood is owing merely to the presence of augmenting matter upon a fixed circumference; this will account but little for the phenomenon. We find that the woody bundles next the circumference are larger and harder than they originally were, and consequently we must suppose that they have the power of increasing their own diameter subsequent to their first formation, and that they also act as reservoirs of secretions of a hard and solid nature, after the manner of the heartwood of exogens. When the growth of the stem of an endogen goes on in this regular manner, with no power of extending horizontally beyond a specifically limited diameter, a trunk is formed, the sections of which present the appearances shown in the accompanying cut. There is a number of curved spots crowded together in a confused way, most thick and numerous at the circumference, comparatively small and thinly placed at the centre; and the only regular structure that is observablo with the naked eye is that the curves always present their convexity to the

Fig. LXIX.

Fig. LXX.

circumference.

When there is no limited circumference assigned by nature to an Endogen, then the curved spots, which are sections of the woody arcs, are much more equally arranged, and are less crowded at the circumference. Never is there any distinct column of pith, or medullary rays, or concentric arrangement of the woody arcs; nor does the cortical integument of the surface of endogenous stems assume the character of bark, separating from the wood below it; on the contrary, as the cortical integument consists very much of the finely divided extremities of the woody arcs, they necessarily hold it fast to the wood, of which they are themselves prolongations, and the cortical integument can only be stripped off by tearing it away from the whole surface of the wood, from which it does not separate without leaving myriads of little broken threads behind.

This is the apparent and general structure of the most perfect among Endogens. It is of course modified exceedingly according to the nature of particular individuals, and may even be reduced to nullity, as is the case in Lemna, Tillandsia usneoides, Naiads, and similar plants.

Schleiden, who treats this subject in a merely anatomical manner, thus describes the peculiarities of Endogens or Monocotyledons, and the manner in which they differ from Exogens or Dicotyledons.

In all plants, he says, the woody bundles, whose development always proceeds from the interior to the exterior, are either limited or unlimited in their growth. Commonly every woody bundle consists of three different physiological parts; firstly, of a tissue of extreme delicacy, capable of rapid development, in which new cells are continually generated and deposited in various ways, in two different directions, viz. next the circumference, in the shape of a peculiar kind of lengthened cellular tissue with very thick walls, the liber; and next the centre, in the form of annular, spiral, reticulate, and porous vessels secondly, of woody cells, which are either uniform in appearance, or different, and form the wood, properly so called. Up to a certain period the development of the vascular system in Monocotyledons and Dicotyledons proceeds upon the same plan; but in Monocotyledons (Endogens) the active, thin, solid, delicate cellular tissue, suddenly changes; the partitions of its cells become thicker; their generating power ceases; and when all the surrounding cells are fully developed, they assume a peculiar form, ceasing to convey gum, mucilage, and other kinds of thick formative sap. From this cause all further development of vascular bundles is rendered impossible, and therefore Schleiden calls the woody bundles of such plants "limited." In Dicotyledons (Exogens), on the contrary, this tissue retains, during the whole lifetime of the plant, its vital power of formation; continues to develop new cells; and so increases the mass, ceaselessly augmenting both the exterior (liber), and the interior faces (wood), for which reason Schleiden calls such woody bundles "unlimited." This, he con

tinues, happens according to the climate and nature of the plant: either pretty continuously, as in Cactaceae; or by abrupt periodical advances and cessations, as occurs in forest trees of Europe. In the latter, the stem forms an uninterrupted tissue, from the pith to the bark, during every period of life, and the bark is never organically separate from the stem; what is considered their natural separation in the spring, is only a rent produced by tearing the delicate tissue already spoken of, which is present, even during winter, and constitutes the foundation of new annual zones, although compressed, and filled with gum, starch, and other secretions. In the spring, being expanded and swollen by the new current of sap, it is deprived of its contents by their solution.