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Proteaceae at Sipolilo Estates, Raffingora, Zimbabwe

My interest is collecting wood in the round - with the bark on. Proteaceae wood resembles that of European Beechwood Fagus sylvatica (Fagaceae) and is characterized by well-defined medullary rays, which are visible to the naked eye. The ray-end pattern is very regular and appears as very fine spindle-shaped marking in the tangential plane.

Medullary rays are the lateral transport lines in plants, extending from the air pores (lenticels) in the bark to the medulla in the centre. Sapwood consists of hollow vessels and tracheids which transport water up the stem: most of the cells in sapwood die immediately after forming the vessels, but the medullary rays contain living cells. Heartwood is older sapwood which no longer transports water, as it is filled with resin or plugged up - heartwood is the plants repository for metabolic by-products. These by-products are transported from the living cells in the phloem and cambium to the centre of the stem by the cells in the medullary rays.

Locally I have gathered samples of dead (seasoned) wood from stumps of:

Faurea saligna Transvaal beach;

F. speciosa Broad-leaf beach;

Grevillea robusta Silky Oak;

Hakea salicifolia Tame Needlebush (used as windbreaks in coffee plantations here);

Macadamia ternifolia Woody Pear (Queensland Nut);

Protea angolensis Northern woodland protea;

P. gaguedi African savanna protea (sparse on the farms of the Sipolilo Estates); and

P. petiolaris Sickle-leaf grassveld protea (ex Great Dyke serpentine soils).

Three views of medullary rays:

A lenticel;

C medullary ray in bast or phloem;

D tangential plane;

E radial plane;

F medullary ray in tangential plane (very decorative);

G medullary ray in radial plane;

H medullary ray in transverse plane;

I sapwood (water-conducting xylem);

K medulla or pith (often hollow);

L heartwood (resin impregnated xylem);

M transverse plane;

N bast or phloem;

O cambium.

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