Olacaceae

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Olacaceae

Description

Trees or erect, rarely scandent shrubs or lianas, sometimes semi- or auto-parasitic. Leaves without stipules, petiolate, alternate, entire, pinnately veined, sometimes with lactifers or resinous dots. Inflorescences axillary, rarely from old branches, short-racemose, paniculate, spicate, often fasciculate. Flowers generally bisexual, actinomorphic, cyclic, 3-7-merous; calyx usually cup-shaped, often very shortly lobed or dentate, sometimes enlarged in fruit; petals free or connate, valvate, caducous, often hairy inside; disc sometimes present, extra- or intrastaminal, consisting of distinct petaloid glands or cup-like, rarely accrescent in fruit; stamens 1-3-seriate, generally free, rarely fused into a tube (Aptandra), epipetalous or partly also episepalous, sometimes in part staminodial; ovary mostly superior, rarely semi-inferior or inferior, usually apically 1-locular and basally 2-5-locular, each cell with 1 usually anatropous ovule hanging down from the free apex of a central placenta, style, if any, conical, columnar, or filiform, with a small, sometimes 3- or 5-partite stigma. Fruit a drupe with a thin, often fleshy pericarp, and a crustaceous to woody endocarp, or a pseudo-drupe (external fleshy layer formed by the accrescent calyx or disc); seed 1, testa, if any, thin, endosperm abundant, embryo minute, cotyledons 2, 3, or 4.

Distribution

Guianas: present Neotropics: present tropics: present
About 180 species in 28 genera, in the tropics; in the neotropics ca. 87 species in 14 genera; in the Guianas 17 species in 10 genera.

IDENTIFICATION


The wood anatomy of the Olacaceae ranges from primitive to specialized. There is no common wood anatomical characteristic for the whole family. One typical feature, not often found outside the Olacaceae, is the vessel- parenchyma pitting, which is of two types in about 60 % of the genera: half-bordered scattered to alternate, similar in shape and size to intervascular pits, and large and simple, solitary or forming a reticulate pattern. In the remaining genera vessel-parenchyma pits are all large and simple. Other characters common to the majority of Olacaceae are the diffuse to diffuse-in-aggregates apotracheal parenchyma and the narrow heteroge- neous rays.
With the wide range of character-states within the family and the limited infra-generic variation, it is possible to separate most genera entirely on wood anatomical characters. For the Guianan genera a key is presented below. TYpe of ground tissue fibres, ray type and presence or absence of vascular tracheids are important characters in this key. These characters require a minute observation. Especially the tangential wall pits in very thick-walled fibre-tracheids are sometimes inconspicuous in tangential sections and may have to be identified at fairly high magnification in transverse sections. Vascular tracheids in Olacaceae are usually associated with the vessels and may intergrade with narrow vessel members. Their abundance may vary considerably in those genera which possess them.
KEY FOR IDENTIFICATION OF GUIANAN GENERAPerforations scalariform in oblique end-walls.2Perforations simple in slightly oblique to transverse end-walls.3Intervascular pits alternate.MinquartiaIntervascular pits scalariform to opposite.MabureaHeisteria (ex. H. scandens)Ground tissue composed of fibre-tracheids.4Ground tissue composed of libriform fibres.7Rays heterogeneous I.Heisteria scandensRays heterogeneous II to Ill.5Vessels predominantly in radial multiples.AptandraVessels predominantly solitary.6Vascular tracheids absent, silica bodies absent.XimeniaVascular tracheids present, silica bodies present.DulaciaAxial parenchyma aliform-confluent.SchoepfiaAxial parenchyma diffuse.8Rays heterogeneous III to homogeneous.CathedraRays heterogeneous II to III.9Silica bodies present.PtychopetalumSilica bodies absent.Chaunochiton

FAMILY CHARACTERISTICS


Vessels diffuse or in a faint oblique pattern, solitary or in radial multiples. Perforations scalariform or simple, intervascular pits scalariform to alternate, large to small, vessel-ray and vessel-parenchyma pits of two types: half- bordered diffuse to alternate, similar in shape and size to intervascu- lar pits, together with large and simple pits; or exclusively large and simple.
Vascular tracheids absent, or scarce to frequent, associated with vessel multiples, sometimes intergrading with narrow vessel elements.
Rays of Kribs' heterogeneous type I, heterogeneous type II to III, hetero- geneous type III to homogeneous, or homogeneous, predominantly 1-3 cells wide. Perforated ray cells present in some genera, not abundant. Parenchyma scarce to abundant, predominantly apotracheal, diffuse or in small aggregates, partly scanty paratracheal; in Schoepfia aliform to confluent.
Ground tissue composed of fibre-uacheids with bordered pits in both tangential and radial walls or libriform fibres with minutely bordered pits mainly confined to the radial walls.
Silica bodies fairly common in ray cells of the genera Dulacia and Ptychopetalum, rarely noted in axial parenchyma cells, predominantly one per cell, occasionally two, surface granular, diameter 10-30 μm.
Crystals solitary rhomboidal, scanty to abundant in chambered or nonchambered ray- or axial parenchyma cells, sometimes absent.

Explanatory note.


The generic descriptions given below are based on many more species than the ones occuring in the Guianas. It is therefore possible that the full range in, for instance, quantitative features such as vessel frequency, ves- sel diameter and element length is not covered by the species in the Guianas.

GENERIC DESCRIPTIONS