Dischidia rafflesiana: Malayan Urn Vine
We have already seen many ways in which plants adapt themselves to their enviroment. Some adaptations, however, are so amazing that they cause us to marvel at nature’s ingenuity and to wonder as to how they came about. One of the most frequent causes for adaptation is the lack (or excess) of water — and it is against drying out that the species is adapted.
Dischidia rafflesiana is found over a large area extending from India to Australia. It grows in monsoon forests that are periodically dry as well as in semi-deciduous forests at higher elevations and during the course of the year it goes through a period when water is in short supply. Striking, at first glance, are the two different types of leaves on the twining stem: the ‘normal’ leaves are fairly small, flat and broadly ovate, the others are sac-like and much larger and on closer inspection are found to be hollow with an opening at the junction with the stem, through which several aerial roots, growing in the axils of the leaves in all members of the genus, penetrate inside the leaf. A cross-section of such a leaf reveals that there is a supply of water stored for the said roots. Whether it is rain water or whether the plant exudes it into the hollow is open to dispute, but the latter seems the more probable.
Similar ‘rooting into itself may also be found in the cultivated species D. merillii, which differs only in the shape of the sac-like leaves and in the plant being of more robust habit. There exist, however, other species with flat ‘normal’ leaves protected against drying out only by a thicker cuticle, for example D. nummularia with small, orbicular leaves, and D. benghalensis with lanceolate leaves, likewise only about 2.5 cm (1 in) long.
All dischidias are grown without any compost, or at the most only on a moss-covered branch. They do best in cases for growing epiphytes and in indoor glasshouses, where they have both ample atmospheric moisture and light. They can also be grown freely in a room, but development, though reliable, is somewhat slower. Propagation is easy — either by seeds or, the more common method, by detaching individual ‘branches’ from the clump or cutting up the stems.