Leaves are opposite and decussate, sometimes show whorled arrangement. The shape of leaf varies and six morphological types have been widely recognised. They are Ovate, Lanceolate, Elliptic, Linear, Big and Small.
Stem is initially green and tender, gradually turns brownish and becomes hard. The bark is reddish brown or dark brown and red inside. Stem is smooth in young trees, turns rough with deep vertical cracks in mature trees. Wood is hard, very close grained, oily. Sapwood is white, scentless, heartwood is yellowish to brown and strongly scented.
Transverse section of young stem is more or less oval. The epidermis is papillose and covered externally witfi thin cuticle. The parenchymatous cortex is distinguishable into peripheral zone of compact cells with chloroplast and an inner zone of intercellular spaced cells. Endodermis is absent. A discontinuous ring of 14-16 collateral, open and endarch primary vascular bundles form the vascular supply to the stem. Each bundle is covered by a patch of thin walled cells which form the discontinuous pericycle. These cells later become lignified and constitute pericycle fibres. The cells of the pith are parenchymatous with inter cellular spaces. The pith cells in the old stem are polygonal in shape and are lignified. Secondary xylem contains growth rings with the early formed wood appearing less dense than late wood could distinguish the growth rings with the help of hand lens during the early stage of growth. However, they could not determine the age of trees by counting these growth rings.
The primary root is moderately long, delicate and flexuose. Lateral roots are moderate in number, fibrous, delicate and distributed down the main root. Roots at an early stage develop nodular growth, the first sign of haustoria. However, A small number of sandal plants does exist without hausorial nodules even upto two years.
The primary root is distinctly diarch, open and exarch. The secondary growth is profuse. The secondary xylem formed; lie in close proximity to that of the primary xylem. The diarch nature of the root becomes indistinct. Structure of the mature root is essentially similar to that of stem. Secondary xylem far exceeds secondary phloem in volume. Tap root system is not deep and lateral root runs almost parallel to the ground and young rootlets produce haustoria which establish connections with neighbouring host roots for absorption of mineral salts. Not all haustoria are functional. Root contains scented oil.
Flowers are purplish brown, unscented and are borne in axillary or terminal cymose panicles. The floral organs develop in acropetal succession. The first to appear are the four perianth lobes followed by epigynous stamens,.carpels and placental column. Flowers are tetra to pentamerous, rarely hexamerous and lermaphrodite. The ovary is semi-inferior and unilocular with three ovules lodged in three depressions at the base: The depressions at the base of the ovary are formed in later stages of development of flower when the embryo sac comes out of the ovule and crushes the cells at the base of the ovary to form small depressions in which the tip of the ovules and the embryo sac rest.
The placental column is straight, generally bearing three, Ovules in hexamerous flowers. However, four ovules are more frequent. The long style is traversed by a narrow canal and terminates in 3 or 4 lobed stigma.
Fruit is a drupe, purplish when fully mature and single seeded. Shapes of fruit vary ranging from round to oblong and sometimes show tapering ends.
Seeds are obtained by removing the fleshy portion of the fruit. They are naked, lacking testa. The dicotyledonous embryo occupies nearly the entire length of the albuminous seed. The endosperm contains 50 to 60 percent of drying oil, protein and mineral matter. The stony endocarp, although not to be called seed coat, is referred as seed coat literally, though it is a false seed coat. Seeds show polymorphic characters, varying in size and shape.
Santalum album is a small tropical tree attaining a height of 4 to 20 meters and a girth of 1 to 2.4 meters. The shape of the leaves vary with six morphological types recognized widely. It may live to more than hundred years of age. The tree is variable in habit, usually upright to sprawling, and may intertwine with other species. The plant parasitises the roots of other tree species, with a haustorium adaptation on its own roots, but without major detriment to its hosts. An individual will form a non-obligate relationship with a number of other plants.