Aristolochiaceae

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Aristolochiaceae

Description

Perennial herbs, more commonly woody at the base, undershrubs or shrubs, erect, scrambling or scandent, sometimes high lianas. Hairs simple, uni- or multicellular, short ones often with a hooked apex. Leaves simple, spiral or alternate, petioled (without an abscission zone), exstipulate; Flowers bisexual, actino-morphic or zygomorphic, solitary, fasciculate, or in axillary or cauligerous, racemose, paniculate or cymose inflorescences, usually only one or two flowers open at a time; Petals (in Mal.) absent. Stamens 6 (4 or 5 in some extra-Mal. Aristolochia 5/7/7.) or 6-c. 36 (-46), in 1 whorl or in 2 (3 or 4) whorls (Thottea); Ovary inferior (rarely half-inferior in extra-Mal. genera), 4-6-carpellate, 4-6-celled, syncarpous (or ± apocarpous in extra-Mal. Saruma); Fruits capsular or siliquiform (follicular or cocci in extra-Mal, genera), 4-6-celled; Seeds many in each locule (1-seeded in extra-Mal. Euglypha), often coated with remains of placental tissue (membranous when dry), horizontal or pendulous, variously shaped;

Distribution

Asia-Temperate: Asia-Tropical: Central and South America: present New World: present South America: present Tropical Africa: present West Africa: present continental Southeast Asia: present northern hemisphere: present northern temperate regions: present worldwide: present
There are 7 genera, Aristolochia worldwide, Asarum over the northern hemisphere, Thottea in continental Southeast Asia and Malesia, Pararistolochia in tropical Africa, and 3 monotypic genera, viz. Saruma in China, Holostylis and Euglypha in South America. As to number of species, Aristolochia is by far the largest with some 300 spp., largely concentrated in the New World, especially in Central and South America, in Malesia with 28 spp.; Asarum (incl. Hexastylis and Heterotropa) with possibly some 70 spp. in northern temperate regions, Thottea with 26 spp., of which 22 in Malesia, and Pararistolochia with 12 spp. in West Africa.

Pollination

Already two centuries ago SPRENGEL suggested insect pollination in Aristolochia and a century ago HILDEBRAND found the flowers proterogynous and concluded to cross-pollination. As a matter of fact the flowers represent a beautiful trap with a 'slide zone' on the limb above the tube which is inside usually provided with retrorse hairs preventing insects to leave during anthesis. They are trapped in the utricle which provides them with nectar and usually also other food substance of glands. BAKER C.S. (1973) added that also stigmatic secretions containing amino-acids would add to the nutritional potential in the utricle. The insects, mostly flies, sometimes also ants, are attracted to the flowers by the putrescent odour, sometimes an offensive smell of decaying meat, emitted during anthesis by the flower or its stalk, and this occurs also in other genera of the family. PETCH (1924) found that some species are visited by only one kind of fly, but in other species he found up to 13 different kinds; the two native Ceylon species were visited by one kind of fly only. In some intricate-built flowers of South American species insects are guided to the sexual organs by a window-pane in the utricle. After the flower withers, and the hairs have lost turgescence, the insects can crawl out, loaded with pollen and can visit another flower, leading to cross-pollination.

This is only a generalization, as it appears from the very large study by PETCH (1924) that there is a great variability among the species: mostly flowers open at daybreak or shortly before and wither after 24 hours, but there are species which show a second-day revival; some have no food bodies; in some species the tube is wide and flies can easily escape; in other species the tube has no hinged hairs. For that reason one cannot give a single answer to whether cross-pollination is necessary for the setting of the fruit in all species.

BURCK (1890, 1892) made extensive experiments, including bagging flowers etc., on three exotic species in the Botanic Gardens at Bogor (viz. Aristolochia barbata, A. elegans and A. ornithocephala = A. brasiliensis) and concluded that they are autogamous. PETCH (1924) studied in detail some dozen species at Peradeniya in Ceylon and concluded that, 'although Aristolochias are adapted for cross-fertilization, some species can be self-fertilised. It is evident that all grades of self-fertility or self-sterility may be expected within the genus.'

Observations on pollination in Thottea are very scant; its flowers are regular and open and do not offer a complicated structure as in Aristolochia. They emit also a putrid smell, are mostly dark-coloured and their flower is also proterogynous, as BACKER (1918) observed in Apama to-mentosa at Bogor. He stated that this species propagates very well vegetatively by stooling and that very few fruits are produced, both in cultivation and in the field in bamboo groves at Depok. BACKER observed flies visiting the flowers; he hypothesized that cross-pollination might be possible during the transition period from the female to the male stage. As a matter of fact I found (1981) the styles or style-lobes (with their stigmas or stigmatic surfaces) reflexed or twisted at an-thesis, facilitating contact with pollen grains, which I found germinated in flowers of Thottea triserialis. Self-pollination and fertilisation may hence also occur in Thottea.

For Asarum reports also vary and both self-pollination and cross-pollination by flies or fungus gnats seem to occur (VOGEL, 1978).

Morphology

Habit. In Malesia there are two main habit types: 1) perennial herbs which are often woody at the base; they are either a) erect undershrubs or shrub-like, up to 3 m high, sometimes slightly higher as in most species of Thottea and some of Aristolochia (e.g. A. humilis, A. macgregorii, A. sericea, etc.) or b) spreading, scrambling or twining up to several metres high, as in Thottea corymbosa and some species of Aristolochia (e.g., A. glaucifolia, A. jackii, A. linnemannii, A. minutiflora, etc.); and 2) woody twiners or high lianas from a few metres up to c. 50 m high, with an old stem up to 2 (-4) cm ø (most species of Aristolochia).

In absence of field data on the habit (erect or climbing) sterile specimens can hardly be identified to the genus (Aristolochia or Thottea). Sterile specimens of erect plants can be discriminated if they are sufficiently ample; see the paragraph 'leaf architecture' under Thottea.

As to the direction of twining, I do not know whether it is constant for the species of Aristolochia. I observed that plants of A. tagala, A. ringens and A. foveolata germinated from seeds and, growing in my office, appear to have no definite direction to twist and may go either right or left as stated by MENNINGER ().

Lianas of Artistolochia twining on high trees bear leaves often at the top and flowers and/or fruits at the lower part of the stem. Occasionally only 'leafless' fertile herbarium specimens were available because the leaves were difficult to locate or to collect.

Roots and rootstocks. The roots, sometimes also root-like tubers, of (some) Aristolochia are fleshy, sometimes with bitter taste, and of various shapes (e.g. globose, ovoid, cylindric, fusiform, turnip-shaped, etc.), which are characteristic for some species. They have sometimes been collected, recorded and used for species delimitation (cf. ). From Malesia nothing is known about root structure.

The recumbent rootstocks or rhizomes of Thottea and some Aristolochia species develop offshoots or runners, which sprawl on the ground or produce erect stems. When the motherplant dies, these stems become free and grow on as separate individual plants, a method of vegetative propagation.

The stems of woody vines of Aristolochia are mostly terete, or sometimes slightly flattened (), and are up to 4 cm or more in diameter. The bark of the old stems is corky and is often longitudinally fissured or prominently ridged or sometimes rather smooth.

On a cross-section one can observe, by using a handlens, conspicuous anatomical features of the Aristolochiaceae: the vascular bundles are arranged in a ring and widely separated from one another by the broad medullary rays. On the cross-section of a rather flattened stem, where the cambium is more active towards two opposite directions, the vascular bundles elongate accordingly and the whole section appears like the numeral '8' (cf. ).

The '8'-shaped appearance of the cross-section of the stem has been used as one of the generic characters for separating the tropical African Pararistolochia from Aristolochia (with circular stem) (cf. PONCY, l.c.). In Malesia old stems of Aristolochia decandra and A. coadunata are sometimes also flattened. .

Leaves. Leaves of Aristolochiaceae can provide useful characters especially for identification of sterile collections. , . However, in some species, they are heteromorphic or very variable in shape, size, texture, etc.; they vary sometimes also between those of fertile and vegetative branches, apical and lower parts of a (high) woody vine, juvenile and adult stages, etc. (e.g. in Aristolochia dielsiana, A. tagala, A. zollingeriana; Thottea tomentosa).

The leaves of Malesian Aristolochia vary in size; the largest known to me occur in A. dielsiana measuring up to 37 by 23 cm; according to R. STRAATMAN they can reach to 100 by 70 cm.

The leaves are usually distinctly petioled. The petiole is often more than 2 cm long, sometimes up to 13 cm; it is very short only in a few species, e.g., Aristolochia macgregorii (c. 3 mm), A. sericea (2-5 mm). In Thottea petioles are usually short.

The leaf does not possess an abscission zone either on the petiole or at its base. The old or dried leaf just hangs on the plant for some time and then breaks irregularly from the petiole, leaving no scar on the stem. This is very characteristic for the species of this family.

The undersurface of the leaf has interesting sculpture features or ornamentation, e.g. hair types or density of hairs, cuticular thickenings or markings, protuberances of epidermal cells, etc., which are useful as diagnostic characters, especially for identification of sterile collections (cf. ). . For example, Thottea dependens has papillae forming rings or curves (), T. muluensis, T. pennilobata, and a few others show crescent, curved or hooked thickenings (), Aristolochia macgregorii has stomata with extended striae of thickenings (). Such characters can easily be examined under a normal binocular with a magnification up to about ×60; sometimes they can even be observed with a handlens.

Also the venation types are often characteristic; the main ones are illustrated in .

Series of axillary buds. In some species of Thottea and Aristolochia sometimes 2 or 3 (-5) buds occur in a leaf axil, especially in the terminal one. These buds may develop into flowering and/or vegetative branches, e.g. in Thottea corymbosa, Aristolochia sericea, A. gaudichaudii, etc. (cf. ).

Flowers. The flower in Aristolochiaceae is probably essentially provided with a calyx and a corolla, but the latter is almost always suppressed. It is still present in the monotypic Chinese genus Saruma which is assumed to be the most primitive of the family. It is also found as 3 rudimentary, subulate segments in Asarum canadense, as a relict feature.

Flowers are very important for species delimitation. Unfortunately, for many Malesian species flowering material is scanty in the herbarium. Some tropical species of Aristolochia have rather large flowers, the largest being the neotropical A. grandiflora Sw., with a limb up to 50 cm wide and a total flower length up to 3 m, a serious competitor of Rafflesia which is mostly held as the largest flower in the world. In contrast with this, Aristolochia flowers have often a thin, delicate texture difficult to handle in dried material.

The flowers in Aristolochia open only one or two, or a few at a time. The flowering duration is often very short, one to a few days. They are sometimes deformed after pressing and drying. The flowers of Aristolochia deliquesce sometimes rapidly; they also fall and decay quickly following pollination and fertilization (cf. ).

The flowers are bisexual; they emerge terminally or laterally in the axils of leaves or bracts, and/or cauligerous; they are solitary, fasciculate, or arranged in cymes, racemes or panicles. The flowering branches or rachides are sometimes with spacious internodes (e.g., Aristolochia jackii, A. schlechteri) or strongly reduced with internodes hardly visible (e.g., A. crassinervia, A. sericea). The flowers are pedicelled. There is often hardly any external distinction visible between the pedicel and the ovary; they have been treated here as one unit.

The perianth or calyx is 3-lobed and actinomorphic in Thottea. In Aristolochia it is rather specialized and usually zygomorphic; it consists of three (sometimes not sharply separated) parts: utricle, tube and limb. Between the perianth and the ovary, there is often a constriction or articulation, sometimes with a lobed rim where the perianth breaks off from the fruit.

The utricle is the basal inflated part of the perianth. It is often globose, subglobose, ellipsoid, ovoid or obovoid. On the inner surface of the utricle, there are usually two symmetrically placed glandular, usually ellipsoid swellings at the apical part. They are food bodies, composed of dense glandular hairs, serving for imprisoned insects (cf. ). Sometimes there are two small bosses or depressions shown on the outer surface corresponding to the position of the food bodies inside (cf. ). Some Malesian species have six such glandular food bodies (e.g., Aristolochia foveolata, A. papillifolia). The distal end of the utricle is gradually or abruptly narrowed into a cylindric tube which may be straight or curved. The base of the 'tube', specially in some extra-Malesian species, slightly elongates and projects into the utricular cavity; the flange-like part inside the cavity has been called syrinx (cf. ). The tube gradually or abruptly and slightly enlarges its size at the apical part and merges with the expanded limb. For the diameter of the tube, only the cylindric, middle part has been taken.

The limb is 1-lipped (in many species), sometimes distinctly 3-lobed (e.g., Aristolochia decandra, A. momandul), occasionally rim-like and obscurely 3-lobed (A. coadunata), or rarely 6-lobed (A. schlechteri).

The colour of the perianth appears sometimes to vary with the developing stage of the flower, as recorded in field notes. It is characteristic in some species. Unfortunately, I could not use it in keys, because it has only erratically been recorded in field notes.

Perianth of Aristolochia. As mentioned above, the perianth of Aristolochia should be regarded as homologous with a calyx and of course be homologous with the perianth in other genera of the family (e.g. Asarum, Thottea). In several species it is also 3-lobed, but in many others it is entire. Some authors have, however, a different opinion about its morphological derivation.

LORCH () observed a shoot of Aristolochia maurorum bearing a series of teratological leaves and proposed a new interpretation of the perianth of this genus. He stated that 'the perianth is the metamorphosed first leaf of a lateral branch' and '. agrees in form with an involute normal foliage leaf.'

HAGERUP () studied both the venation and the development of the leaf and the perianth of Aristolochia (especially A. elegans). He concluded that 'The perianth is not compounded of several united leaves but consists of only a single leaf (like the spathe of the Araceae).'

GUÉDÈS () and TIONG CHUI HUONG () made comparative, morphological studies on the vegetative leaf and the perianth of Aristolochia (e.g., A. clematitis, A. grandiflora, A. peltata). Their results confirmed the interpretation and findings of LORCH and HAGERUP.

It should be remarked that the Aristolochia species, studied morphologically and anatomically by the three authors all possess a 1-lipped perianth. Their thesis should be tested for species in which the limb is rim-like or obscurely 3-lobed (e.g. A. coadunata, A. griffithii), or distinctly 3-lobed (e.g. the tropical West African species of Pararistolochia; and A. decandra, A. momandul), and the 6-lobed species A. schlechteri.

Stamens and styles. The number and arrangement of the stamens in Thottea show an interesting series of reduction. . The stamens in this genus range from 36 (-46) (e.g. T. grandiflora) to as few as 6 (e.g. T. tomentosa)', they are from free and arranged in 4 series (T. parviflora), through partly free and in 3 (T. triserialis) or 2 series (most of the species), to united with the style column and just in 1 series (several species, e.g. T. corymbosa).

In Aristolochia the stamens are adnate to the style column to form a gynostemium. All Malesian species have 6 stamens, except A. decandra which has 10. . Each anther consists of two thecae with four microsporangia (pollen sacs) (cf. ). The thecae of a stamen are in some Aristolochia species (e.g. A. jackii) separated from each other by a rather broad connective.

The styles appear to be free in Thottea parviflora. They are united with the stamens into a short column (gynostemium) in all other species of Thottea and Aristolochia. The style column may be discoid or obtuse at apex and then divides, or sometimes redivides, into a number of slender or finger-like lobes. The number of styles or style lobes varies in species of Thottea from c. 20 (e.g. T. macrophylla) to only 2 or 3 (e.g. T. paucifida; ). In Malesian Aristolochia the style has 6 lobes (except 3 in A. coadunata and 10 in A. decandra).

The lobes of style column (or gynostemium) are glabrous (often sticky when fresh) or sometimes (densely) hairy (covered with hooked and/or straight hairs or papillae). In Thottea, they are erect or spreading when young and often reflexed or irregularly twisted at anthesis (cf. ).

In Aristolochia, changes occur in the structure and shape of the style lobes at anthesis. When young, they are distinctly separate from one another. At first the style lobes may be rather thin with longitudinally reflexed margins and their basal parts covering the apices of the unopened anthers. At anthesis, the style lobes slightly swell, flatten, and become erect and adherent; their apical parts bend inward, and the anthers become exposed. The lobes form then almost a funnel; their apical parts and inner surfaces have a rather thick layer of slime (cf. ).

In herbarium specimens of both Aristolochia and Thottea I observed that the style lobes are sometimes covered with pollen grains which even may have germinated. These lobes certainly possess stigmatic surface. However, some botanists assume that the lobes are not true stigmas, and that the connectives of the anthers have assumed stigmatic functions (cf. ). This idea seems a bit far-fetched, as for example Aristolochia coadunata has only 3 style lobes, but the usual 6 stamens. Also in Thottea the number of stigmatic lobes does not correspond with the number of stamens; in T. tomentosa, with 6 stamens the number of lobes is 3 or 4.

Ovary and placentation. The ovary is inferior (but half inferior in extra-Malesian monotypic Saruma and some species of Asarum). It is linear, cylindric or fusiform, and is 4- to 6-carpellate and syncarpous (apocarpous in Saruma).

The placentas are parietal when young and gradually become imperfectly 4-6-celled. Whenever I dissected a flower, I observed that the placentation appears to be axile. The pseudo-axile appearance is due to intrusion and fusion of the placental partitions in later stages (cf. ).

The ovules are anatropous and bitegmic (cf. ). They are usually numerous and are horizontally or pendulously superposed in one or two series in each locule of the ovary.

Fruits and seeds. Fruits and seeds are very characteristic for the Aristolochiaceae. The fruits are usually capsular (e.g. Aristolochia; ) or siliquiform (Thottea; ) (but follicular in the extra-Malesian Saruma and cocci in Euglypha). They are 4-6-loculed, usually dehiscent, septicidal, acropetal (and the opened, hanging fruit basket-like as characteristic in Aristolochia; ), or basipetal. They are indehiscent in the tropical African Pararistolochia and possibly also in the New Guinean Aristolochia dielsiana (see there). They are usually glabrous or rarely hairy (Thottea) (cf. ).

The size of the fruits is very variable: in Malesian representatives: the length ranges from c. 1 cm (e.g. Aristolochia sericea) to 20 (-38) cm (e.g. A. dielsiana; Thottea tricornis) and the width from c. 0.5 cm (Thottea) to c. 4 cm (Aristolochia).

The fruit wall is often slightly lignified (but strongly lignified in Pararistolochia and some Aris-tolochia species). The valves of the capsules in Aristolochia can sometimes easily be separated in epi-, meso- and endocarp.

The seeds are usually numerous, horizontally or pendulously superposed, and immersed in the spongy cellular tissue in each locule of the capsules (but only one seed developed in extra-Mal. Euglypha). They may be divided into two main types according to their general appearance: 1) compressed and flat (Aristolochia, Asarum and Holostylis) and 2) oblong, fusiform, or broadly ovoid, obscurely or distinctly triangular (Thottea). . However, the flat seeds sometimes may be longitudinally slightly or strongly concave (e.g. Aristolochia singalangensis; Thottea curvisemen and Thottea sp.).

The seeds are not winged or with a rim-like or marginal wing (Aristolochia). They are often slightly or prominently transversely corrugate or rugose (Thottea) and are smooth or warty on the testa (Aristolochia). The irregular surface of the testa in Aristolochia is due to unequal divisions and outgrowth of the epidermal cells (cf. ).

In Aristolochia the seeds in many species have an almost unique feature in that the large funicle is rather fleshy, thick, dilated laterally, flattened against the upper surface of the seed and generally larger than it (). This fleshy funicle is equivalent to an elaiosome and is important in seed dispersal. In the dry state it becomes almost membranous and usually covers the seed ().

In Thottea, after the coating membranous tissue is removed, the testa cells appear as reticulations or papillae; each of these cells has a strong thickening projecting into the cell lumen. If the soft tissue of the testa has been removed or brushed off, one can easily observe the two layers of crossed fibres of the tegument (cf. ). .

According to CORNER (l.c.) the attachment of the integument along the course of the raphe and the development of two layers of crossed fibres in the tegument forming the mechanical layer of the seed coat are the chief characters of the seeds in Aristolochiaceae. He also stated that the tegument of Caricaceae seems strikingly similar to the one of this family in having the same set of crossed fibres.

The endosperm of the seeds in Aristolochiaceae is copious and fleshy. The embryo is minute with two distinct cotyledons and is enclosed in the endosperm close to the hilum (cf. ).

Seed germination and seedlings. The seed germination of some species of Aristolochia and Asa-rum (s.l.) has been reported as epigeal, with the cotyledons spreading above the ground.

In Aristolochia, during germination, the radicle protrudes through the hilum or near it or through the testa. The cotyledons are rather fleshy, suborbicular or broad-ovate, with simple venation (midrib with a few lateral nerves or veins). The first two leaves are opposite; they develop from almost the same plane as the cotyledons and are at right angles with them. The foliage leaves, following the first pair mentioned above, are scattered (cf. ).

Seed dispersal. The winged seed of some Ahstolochia species may help in dispersal. More important seems the elaiosome (fleshy funicle) which is probably attractive to ants.

Anatomy (for oil cells, silicified cells and crystals see under Phytochemistry). METCALFE & CHALK (1950) provided a general survey of the vegetative anatomy of the family: hairs simple unicellular or uniseriate and / or with a hooked terminal cell with silicified tip ('bracket hairs'). Stomata usually anomocytic. Stems typically with broad medullary rays. Secondary phloem occasionally with stone cells but devoid of fibres. Wood with very wide vessels in climbers, but rather narrow ones in erect species. Vessels with simple perforations and coarse pits. Fibres with bordered pits (especially conspicuous in Aristolochia). Parenchyma paratracheal, often scanty. Rays mostly wide and forming broad interfascicular bands, but narrow (up to 3-seriate) in some species of Apama (= Thottea), heterocellular. GUÉDÈS (1968) described the petiole anatomy of some Aristolochia species; ALEYKUTTY& INAMDAR (1980) provided detailed accounts of hair types in the family; PHILIP (1983) reported on the diverse ontogeny of the stomatal complex in species of Aristolochia and on the predominance of paracytic stomata in Aristolochia leuconeura.

Vegetative anatomy is in agreement with the view that Aristolochiaceae are related to the Magnoliales.
— P. BAAS.

Taxonomy

Though certainly natural, the family is rather heterogeneous: small creeping or erect herbs and large woody lianas, flowers regular or zygomorphic, stamens 6 to many, perianth simple or double, etc. Several genera have outstanding structures: Asarum has a leathery capsule bursting irregularly, Aristolochia has a bent, zygomorphic complicated flower, the curious South American genus Euglypha has also a utricle but not a bent flower and besides has a fruit consisting of 6 one-seeded cocci attached to a sort of columella, the South American genus Holostylis is like Aristolochia in flower, but its flower is also straight and does not possess a utricle, Thottea has up to 4 whorls of stamens (up to 36-46), and the Chinese genus Saruma has a double perianth and 6 halfway free follicles.

Whether the West African genus Pararistolochia can be maintained is liable to doubt. KEAY () distinguished it from Aristolochia by: 'Fruit indehiscent, elongated, strongly ribbed, cucumber-like', but these characters seem also to occur in the New Guinean A. dielsii SCHMIDT (see p. 105). — Editor.

Affinities. In the past many suggestions have been made and there is unanimity that most characters point to the assemblage of primitive families in the Dicotyledones, especially through those of the genus Saruma. Since WAGNER'S research () the general opinion prevails that among the living plants the closest affinity is with Annonaceae in the general Magnoliales concept.

Cytology

In Aristolochiaceae, chromosome data have been reported for about 90 species of mainly the two (large) genera, viz. Aristolochia and Asarum (s.l., incl. Heterotropa and Hexastylis) and only one species of Apama (= Thottea).

In Aristolochia the somatic chromosomes have been reported as 2n = 8, 10, 12, 14, 24, 26, 28, 32. The number in this genus is, with some deviations, rather uniform: 2n = 14 (in most of the tropical species) and 2n = 28 (in most of the temperate zones) (cf. GREGORY, 1956). There is one widely distributed species, occurring also in Malesia, A. tagala, having 2n = 14; I examined the material of this species from Celebes and New Guinea and obtained the same number. The other numbers occur very unfrequently: 2n = 12 (or 24) four times, 2n = 8, 10, 16, 32 each once, mostly for extra-tropical species.

In the extra-Malesian genus Asarum (s.l.) the chromosomes of many species have been reported mostly with 2n = 24 (for Asiatic species) and 2n = 26. There are only a few species with 2n = 36, 40, or 48.

For the genus Thottea, there is only one species of Apama (= Thottea) from India being known with 2n = 26 (cf. FEDOROV, 1969).

There is still no chromosome information known for the three monotypic genera, viz. Euglypha, Holostylis and Saruma.

Uses

Some American Aristolochia species are cultivated for their (rather large) beautiful flowers as ornamentals, e.g. A. brasiliensis MART. & ZUCC., A. elegans MART. & Zucc, A gigantea MART. & Zucc, A. grandiflora Sw., A. ringens VAHL, etc.

In Malesia some indigenous Aristolochia and Thottea species are locally cultivated as food plants for the larvae of the beautiful (swallowtail) butterflies, for commercial purposes.

Some members of the Aristolochiaceae have been used for drugs, medicine, or medicinal products, especially in the Far East and Southeast Asia. According to published records, such plants or their derivatives have been applied to remedy snake bites, stomach-ache, dysentery, rheumatic affections, colds, headache, toothache, or to reduce swellings and high blood pressure, etc. Aristolochic acid has been reported possessing the capacity to reduce growth of certain types of cancer in mice. For medicinal uses of Malesian plants see the records under the species concerned. For further details one should consult the following literature.

Phytochemo

The chemical characters of Aristolochiaceae have been summarized and discussed from a taxonomic point of view by HEGNAUER (1960, 1964) and a comprehensive phyto-chemical review of the family was given by MUNAVALLI & VIEL (1969).

Members of the family tend to deposit SiO2 and calcium oxalate in their tissues. Heavy silicifi-cation of cell walls (hairs, epidermis, mesophyll) and cell lumina (silica bodies of various shapes) is especially frequent in the tropical members of the three genera in Malesia. Calcium oxalate occurs in the form of prismatic and needle-shaped crystals which are accompanied or replaced in species of Aristolochia by druses.

All members of the family possess oil cells producing appreciable amounts of essential oil of taxon-specific composition. These idioblasts occur in roots, rhizomes, leaves and flowers. Depending on taxa and chemodemes monoterpenes, sesquiterpenes or (and) phenylpropanoids are the main constituents of these essential oils.

The nitrophenanthrenes called aristolochic acids and debilic acid and the biogenetically related phenanthrenoid aristolactams occur practically everywhere in Aristolochia and have been traced in species of Thottea and Asarum.

Consideration of the chemistry leads to the conclusion that the affinity of Aristolochiaceae is closest with Annonaceae as suggested formerly by VON WETTSTEIN. The most convincing evidence comes from the co-occurrence of heavy silification, essential oil in idioblasts and benzylisoquinoline alkaloids and their degradation products. Both families should be included in Polycarpicae (compare, e.g., Magnoliiflorae, DAHLGREN, 1980).
— Editor's extract from a large report of R. HEGNAUER.