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Seeds

One useful feature that is not immediately available in the field is the seeds. Until the vascular connections between the individual fruits held in the crown and the parent tree are broken, the valves will not open. Otherwise, eucalypt fruit are held on the branchlets often for years. Seed from detached fruits, however, can be ready for inspection after about 24 hours by placing unopened fruits in a paper bag where they dry out quickly and shed the seeds and the thinner chaff particles. There is a great number of seed forms and these can be seen either with the naked eye or by means of a lens. Fortunately, related species have identical seeds and the character is therefore one of high reliability. Because words do not adequately convey the actual seed shape for most species, experience is needed to educate the user who will ultimately find the seeds to be an invaluable aid in discriminating species and groups of related species. We suggest the following terms as a guide.

Flattened or saucer-shaped
The seed is somewhat flattened with a distinct upper (dorsal) and lower (ventral) side. The ventral side may be somewhat concave, with the hilum in the centre. Angophora and the ghost gums have this type of seed.

 

Pyramidal or obliquely pyramidal
The seed is pyramid shaped with a relatively smooth or lacunose, flat or rounded dorsal side. The ventral side is usually ribbed, wrinkled or angled and is surmounted by a narrowed face at the summit where the hilum is (e.g. E. acmenoides). This is the seed type in most of the monocalypts although there is a great amount of variety in their seed form. Perhaps the most extreme seed shape in the monocalypts is seen in some western endemics, e.g. E. buprestium and E. todtiana, in which the body of the seed is small in comparison to the grossly extended curved lateral wings.

Boat-shaped
The seed is elongated and strongly keeled dorsally with a large, conspicuous hilum in the middle of the flat underside. The edges may be flanged or narrowly winged. E. gummifera and E. calophylla notably have this type of seed.

Cuboid
The seed is chunky, often with a smooth, shiny or somewhat granular, sometimes slightly rounded, dorsal side. The hilum is situated on a smaller terminal face separated from the dorsal side by the side walls of the seed. These walls are often angular. The chaff is usually similar to the seed, but somewhat smaller and lighter coloured (e.g. E. seeana).

Ellipsoidal with terminal wing
The flattened-ellipsoidal body of the seed occurs at the lower end (considering the disposition of the ovule on the placenta in the intact bud), with a transparent wing as long as the body of the seed at the top end. Overall colour of the seed is reddish or yellowish brown. The wings may be seen, just before seed shed, emerging from the top of the ovary. The hilum is usually positioned near one edge not far from the start of the wing. The wing is purely a descriptive morphological term and the structure has no apparent aerial function. Most of the bloodwoods have this type of seed (e.g. E. chippendalei).

Pointed at one end
The seed is somewhat flattened, usually rounded at one end and pointed at the other. It may be described as teardrop-shaped (e.g. E. conica).

D-shaped
The seed is roughly disc-like with a short straight side and a longer connecting curved side. The hilum is towards the narrowed end (e.g. E. porosa).

Spherical
The seed is more or less spherical (e.g. E. desmondensis).

Ovoid or depressed ovoid
The seed is ovoid or elliptical in outline but flattened with the hilum on the more or less concave ventral side (e.g. E. aggregata). A large number of species have this type of seed which are otherwise difficult to describe. Examples are the section Maidenaria, endemic to eastern Australia, in which the dorsal surface is often lacunose, and a large number of mallees occurring across southern Australia. These seeds have very smooth dorsal sides with two or three shallow longitudinal grooves. This is seen particularly in series Subulatae and Calycogonae.

Obliquely elongated: the seed is like a narrowly drawn-out pyramid with the dorsal face curved and prolonged into a thin "tongue". The terminal face is small, flat and oblique on the seed with the hilum in the middle. The sides are ridged (e.g. E. burracoppinensis).

Linear
The seed is narrow and elongated, with a very small dorsal surface, long sides and terminal hilum (only E. curtisii).

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