Morus – Mulberry.
In family Moraceae the Morus genus has about 13 (10 – 16) species.
Morus alba, M. rubra and M. nigra are three of the better known ones.
There are also a number of cultivars.
Among their numerous uses are as a fruit (especially M. nigra), as ornamentals
and for raising silkworms (M. alba).
Morus nigra.
Cultivated in Australia, it is a deciduous tree to 15 m high and 7 m across.
The gnarled trunk is relatively short and the bark is dark grey and stringy.
The rounded crown is dense.
There are hairs on the small branchlets.
The thick, dark green leaves to about 12 cm long are alternately arranged.
They are on stalks to 2.5 cm long and there are free stipules.
Leaves are mainly simple and widely ovate or heart-shaped.
Blades may also be lobed to various degrees and the edge has blunt teeth.
There are 3 to 5 main veins radiating from the base.
There are a few hairs along the veins on the green upper surface.
The paler lower surface has a more hairs, also along the veins.
Some trees have both male and females flowers, others are either male or female.
The sex of a tree can change.
Axillary inflorescences are spike-like with many small, closely packed flowers.
They grow from new or old wood and are on short stalks.
They are drooping with the males to 4 cm long and the female to 2.5 cm.
Male flowers have 4 sepals (tepals), no petals and 4 stamens opposite the sepals.
They produce masses of wind dispersed pollen.
Greenish female flowers have no stalks.
They have 4 sepals (tepals) that become swollen and fleshy after pollination.
There are 2 (3) fused carpels in the superior ovary.
One carpel is usually rudimentary leaving 1 (2) locule with 1 apical ovule.
The 2 (3) styles are very short but sometimes absent.
The stigma has 2 branches with papillae or hairs.
The fruit is a multiple fruit composed of all the small fruits in the spike.
Each individual fruit consists of the fleshy calyx lobes and a single hard seed.
Despite the name they are not berries.
The fruit ripens from green to pink to purplish-black.
J.F.
