Climbing is one of plants’ knackiest inventions.
Leaves are their little solar power stations, and the more of them it can place in sunny positions, the better the plant grows. You know the story, I’m sure. Using solar energy, leaves convert carbon (from carbon dioxide in the air), and hydrogen (from water, which is made of hydrogen and oxygen) into carbohydrates. They release lots of lovely oxygen in the process, and use the carbohydrates for body-building and the energy to do it.
In a crowded environment with a dense canopy, new little plants may never be able reach enough light. Many wither on the forest floor.
Rainforests are called “vine forests” for a good reason, though. All sorts of quite unrelated plants have evolved into vines. Climbing has given them the ability to acquire height quickly. Because they use other plants for support, they don’t have to spend time and energy building their own trunks. Therefore they can compete effectively for a share of the sunlight, at a much earlier age than a seedling tree, germinated at the same time, could ever do.
They use a lot of different techniques. Some just scramble, poking lots of little branchlets among the foliage of other plants to support themselves. Some use thorns to hang on. Some twine their stems around any support they can find - I have even seen a blood vine twining up a strong strand of the web of a golden orb spider.
Some have developed specialised twining organs, called tendrils.
All those methods depend the climber finding suitable bits of vegetation to grab.
Just a few plants have bypassed all that, and climb straight up the trunks of giant trees. Most of them do it with clinging roots, produced along their stems.
Cayratias, like a very few other members of the grape family, have a very specialised way of achieving it. They have adhesive discs on the ends of their tendrils.
Some of their overseas relatives like Boston ivy Parthenocissus tricuspidata (which is really a kind of grape, not an ivy at all) and Virginia creeper (P. quinquefolia) have found a special place in gardens because of this ability. They can climb on masonry, so are used to ornament brick walls and buildings.
Our local soft water vine can probably be used in the same way. Plants with clinging tendrils have the advantage over root-climbers like ivy, in that they restrict themselves to the wall’s surface, rather than sending questing roots into mortar and tiny cracks, to grow and break the wall apart.
The soft water vine can also be grown on trellises and pergolas.
It is an attractive foliage plant, one of the few local examples of plants with "pedately compound" leaves. Note how the stem first divides into three, then two of these divisions divide into two. This distinctive style of leaf makes it easy to identify in its native rainforest habitat.
Soft water vine has large bunches of tiny white flowers, and bird-attracting little black “grapes”.
It is frost tender, and can tolerate heavy shade (which means it can also be used indoors, as a pot plant).