Crypteroniaceae

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Crypteroniaceae

Description

Evergreen trees. Leaves with minute or rudimentary stipules, opposite, simple, entire, penninerved, shortly petioled, with arched or almost straight nerves mostly anastomosing in a marginal vein. Inflorescence terminal or axillary, sometimes below the leaves, paniculate, copiously branched to extremely depauperate, branched up to the third order, with decussate side axes which are sometimes arranged (sub)-verticillately or subumbellately by contraction, either ending in profuse to very poor racemules, or in cymoid florescences. Flowers (very) small, shortly pedicelled, bisexual, sometimes by reduction unisexual and then trees dioecious, actinomorphous, peri-to epigynous, (4-)5(-6)-isomerous, sometimes with twice the number of stamens; Sepals valvate, triangular to deltoid, mostly persistent. Petals more or less rudimentary, sometimes absent, alternisepalous, inserted on the margin of the receptacle, inflexed and enveloping the stamens, valvate, rarely imbricate, sometimes cohering, soon caducous. Stamens if isomerous epi-petalous, (alternisepalous), inserted on the margin of the receptacle, inflexed in bud, persistent or caducous; Ovary superior or inferior, 2-4(-5)-carpellate, 1-6-locular, septs not, or rarely partly, connate; Ovules situated in horizontal or vertical position, 1, 2, 3, or many per locule, anatropous; Fruit superior or ½- or ¾-inferior, a chartaceous or woody capsule, subglobose to ellipsoid, small to big, loculicidally dehiscent with 2-6 valves, on the top often with the persistent style and stigma. Seeds few or many, flat, usually small, depressed-ellipsoid, situated basally, apically, centrally, or laterally in its membranous wing in which the raphe is running freely;

Distribution

Asia-Tropical:, Borneoendemic Indo-Malesia: present Pantropical: present S. Africa: present Southern America:, Bolivia (Boliviapresent); Peru (Perupresent)
Pantropical, 5 genera and 11 spp., 3 genera in Indo-Malesia (of which one endemic in Borneo), one monotypic genus in S. Africa (Rhynchocalyx) and one in Peru and Bolivia (Alzatea).

Morphology

In all genera the nodes of the twigs are thickened and a characteristic transversal ridge or line, sometimes faint (absent in Rhynchocalyx), connects the leaf-bases. On the internodes four lengthwise raised lines or narrow wings occur, especially distinct in the upper part of young twigs; they wear off later.

The leaves offer no significant characters, but interesting is the occurrence of ephemerous rudimentary stipules which can only be observed on innovations. These are common among Myrtalean families, but obviously absent in Melastomataceae, where these structures were not found in a sampling of fifteen genera.

The petals in Crypteroniaceae are reduced to a varying degree or are even totally absent (in Crypteronia). Moreover, they are always soon caducous, except in Alzatea where they are almost invisible and mucilaginous. In all genera they are conduplicate and enveloping the inflexed stamens as a hood. In Dactylocladus and Rhynchocalyx they are minute and unguiculate; in Axinandra they are proportionally bigger, and have a broad instead of an unguiculate base. The petals of Axinandra are complicated and show a highly interesting specialization; they are coherent to connate, together having the shape of an umbrella or a mushroom. Their wide, tapering basal parts together form the awning of the umbrella, the narrow, coherent, median parts form the stem of the umbrella, and often there are wider, frayed, reflexed, apical parts of the petals together forming the handle of the umbrella (or the 'root' of the mushroom). This whole structure envelops the stamens very closely, and drops when the flower opens and the inflexed stamens stretch. It is, furthermore, interesting that these petals of Axinandra, depending on the species, can be valvate-connate, valvate- (or somewhat imbricate-)conduplicate, or imbri-cate-contorted.

Several petal characters of Crypter oniaceae are found again scattered in other Myrtalean families. Reduction, absence, as well as caducousness of petals occurs sporadically in almost all of these families. Unguiculate petals are more or less characteristic for Lythraceae, but are also found in Sonner atiaceae (Duabanga), and in Rhizophoraceae (e.g. Car allia). Connate petals with a broad base, sometimes fused to a 'cap' occur in Myrtaceae. Coherence of petals is also present in Rhizophoraceae (Ceriops). Valvate and imbricate petals, both found in one genus, Axinandra, are usually family characters in Myrtales. Contorted petals are, apart from Axinandra, only found in Melastomataceae.

The enveloping of the stamens by the petals in all petal-bearing Crypteroniaceous genera is almost unique in Myrtales, being only found in a few Rhizophoraceae (Rhizophora and Bruguiera). However, in the latter family the petals do not cover the stamens as a hood, as is the case in Crypter oniaceae. This is one of the characters upon which the identity of Crypter oniaceae as a family is based.

The stamens in Crypter oniaceae are arranged in one isomerous epipetalous (alternisepalous) whorl, except in Axinandra, where one diplostemonous whorl is present. In general number and position of the stamens in Myrtales can be derived from a situation with two isomerous whorls, either by reduction or by polymerisation ('dédoublement') and multiplication. Arrangement of stamens in two isomerous whorls, the diplostemonous androecium, is mostly considered to represent the basic structure of the androecium in Myrtales. MELCHIOR (in Engl. Syllabus 2, 1964, 345) distinguished for the androecium in Myrtales two progressive trends both starting from the diplostemonous androecium, viz multiplication into many stamens in many whorls and reduction towards the haplostemonous state and even eventually to 3, 2, or 1 stamen(s).

In all Crypteroniaceous genera the stamens are inflexed in bud. This is a widespread character in Myrtales, being rather typical for this order. In some families (Myrtaceae, Rhizophoraceae) it is not present in all genera, and Lythraceae, Onagraceae, and Haloragidaceae are the only families in which it is totally absent. The total absence of inflexed stamens in the Lythraceae is another fact which militates against inclusion of Crypteroniaceous genera in that family.

The gynoecia of the Crypteroniaceous genera are distinguished by cells which are divided by interrupted septs, though these may touch each other in the centre of the gynoecium. This (hemi)synplicate condition is very rare and assumed to be primitive within the Myrtales, in which it is only found in Crypter oniaceae and in a few genera of Myrtaceae.

The capsules of Crypteronia and Axinandra show interesting specialized structures with a functional significance with regard to opening and closing of the capsule. The mechanisms for this are based upon hygroscopical properties of fibres in vascular bundles.

The morphology of the seed in the Crypteroniaceae is peculiar. The seed-coat forms a flat, membranous wing, through which the raphe is running from the insertion to the top where it usually takes a more or less sharp turn, and runs back towards the seed proper, which either takes a central, apical, lateral, or basal position in the wing. This is another assumedly primitive character within Myrtales, again only found in Crypteroniaceae and in a few genera of Myrtaceae.

This character is also rare in other orders. It was first discovered in the Trochodendraceae and is, therefore, indicated by me as the Trochodendraceous seed type.

Summarizing, we find that almost the whole variety of floral characters in the Crypteroniaceae is also found scattered in other Myrtalean families. In this respect the Crypteroniaceae are rather heterogeneous, though not more than for instance the Myrtaceae and the Melastomataceae. On the other hand, the family is unique in the Myrtales by having petals enveloping the stamens as a hood. Moreover, the presence of one whorl of epipetalous (alternisepalous) stamens, characteristic for four out of the five Crypteroniaceous genera, is very rare in other Myrtalean families, being restricted to one or two genera of the Myrtaceae and of the Lythraceae, and to the mono-typic Oliniaceae. Finally, the conduplication of the connective or the tendency to it in all Crypteroniaceae except Dactylocladus, is another important family character, in other Myrtales only found in a few Melastomataceae. Apart from the above-mentioned characters Crypteroniaceae are also characterized by the septation of the gynoecium and by the Trochodendraceous seed-structure, both being only found in other Myrtales in a few Myrtaceous genera. They are, however, from a practical viewpoint, less useful for easy diagnosis. — C. F. VAN BEUSEKOM.

Anatomy

VAN VLIET, . These two papers contain a full bibliography to the older literature.

The anatomy of Crypteroniaceae sensu lato is heterogeneous. Distinctive characters are: cuticle granular (Axinandra, Crypteronia) or smooth (Dactylocladus); stomata paracytic (Axinandra, Crypteronia) or anomocytic (Dactylocladus); hypodermis present (Axinandra, Crypteronia) or absent (Dactylocladus); petiole with arc-shaped vascular bundle (Axinandra) or with ± closed system (Crypteronia, Dactylocladus); phloem with styloid crystals (Axinandra, Crypteronia) or crystal sand (Dactylocladus); cork arising in pericycle (Axinandra, Crypteronia) or subepidermal (Dactylocladus); node complex, with complete girdling trace (Axinandra, Crypteronia paniculatd) or with common gaps (other species of Crypteronia, Dactylocladus); cortical bundles present (Axinandrap.p.) or absent (other taxa); vesturing of vessel pits in wood confined to the pit chamber (Axinandra, Dactylocladus) or also on pit apertures (Crypteronia); vessel-ray pits alternate (Axinandra, Crypteronia) or reticulate to scalariform and larger (Dactylocladus); parenchyma aliform with narrow wings (Axinandra, Dactylocladus) or chiefly diffuse in aggregates (Crypteronia); rays heterogeneous Kribs type I (Axinandra, Crypteronia) or Kribs type III (Dactylocladus); intercellular canal-like spaces present in rays (Crypteronia, Dactylocladus) or absent (Axinandra).

The entire evidence from vegetative anatomy supports affinities between Crypteronia and Axinandra — both genera sharing salient features with a number of Melastomataceae. Dactylocladus resembles several Melastomataceae in its anatomy more closely than it does Axinandra or Crypteronia. The inclusion of Alzatea from S. America and Rhynchocalyx from S. Africa in the Crypteroniaceae adds to the anatomical heterogeneity of the family. On anatomical grounds, Rhynchocalyx fits better in Lythraceae, and Alzatea could also be accommodated in that family with its trilacunar nodes as only aberrant character. The existence of a considerable overlap of the anatomical range in Melastomataceae with that of Lythraceae, Sonneratiaceae and Oliniaceae, forbids, however, formal taxonomic decisions on anatomical grounds only. — P. BAAS.

Taxonomy

Crypteroniaceae belong undoubtedly to Myrtales. Though the family concept in this order is fairly satisfactory, it can be observed from the above-made remarks that there are not many exclusive characters, most of them breaking down occasionally in one family, or occurring also sporadically in another family. Each family in Myrtales seems to be characterized by a unique character combination in addition to one or two exclusive characters.

For Crypteroniaceae this combination and characters are: swollen nodes with transversal line, internodes with lengthwise raised lines or wings, petals in bud hood-like enveloping the stamens, soon caducous (in Crypteronia absent), stamens inflexed in bud and in one epipetalous whorl (except in Axinandra in two whorls), absence of a perianth tube or of any space between the insertion of petals and stamens, and furthermore the presence of a (hemi)synplicate gynoecium and seeds of the Trochodendraceous or related type, both assumedly primitive characters, and almost exclusive within Myrtales.

Palynological evidence does not fully sustain the recognition of Crypteroniaceae as a distinct family; it could be accepted, but the evidence may allow other possibilities ().

Anatomical evidence is not much in favour of the family concept as proposed; the genera could in this respect be divided up among Melastomataceae and Lythraceae, but it remains to be seen in how far anatomical characters clearly sustain other current family concepts in Myrtales.

Myrtales are certainly a very ancient complex and during their evolution advanced characters have evolved, reduction series occurred in more lines, and primitive characters may have incidentally persisted in various branchings of ancestral tree in taxa which are not necessarily viewed as closely related. This would also explain the 'reticulate character distribution', a condition found in several families of Myrtales.

None of the Myrtalean families is really homogeneous, but from this can and should not be concluded that these families are unnatural. For tracing ancestry and evolution naturalness is more important than homogeneity which, properly, increases always with decreasing taxonomic rank.

The main subdivision of two subfamilies is supported by wood-anatomical characters (), but other anatomical characters () and palynological data (MULLER, l.c.) do neither support it, nor militate against it. At tribal level morphological, anatomical and palynological data appear not to agree. The subdivision adopted here is based on morphology. — C. F. VAN BEUSEKOM.

Uses

Crypteronia paniculata, which may attain a height of 30 m, is said to have durable, reddish heartwood and is sometimes used in West Java for house-building; also in S. Sumatra reports are favourable (), but occurrence is too scattered to have come into general use.
Dactylocladus stenostachys is one of the most important export timber trees of Sarawak and Sabah; see under that species.