It's just seeking a damp tree trunk to latch onto with its aerial roots, so it can climb and eventually develop those monstrous 2-foot-wide leaves.

Why is this one white and bulbous, though?

who would have thought the deign on that tablecloth would make it almost impossible for me to focus on the part you want me to look at ...

or its just out of focus because it focused on the design ...

just noting the weird camera trick...

plant do weird things.. what more do you want.. or can i say ..

ken

Is this just white because the papers were keeping the light from reaching it? Yes. Depriving certain areas of plants of light is called blanching. It is an effective method of predisposing the plant to produce root initials or (in this case) to activate existing root primordia to grow. I use it along with a growth hormone to considerably hasten the process of air layering. If you pr others have interest in learning how to put blanching to work, just ask and I'll go over some methodology. It really is a slick trick.

Does it need to stay covered? I can't say precisely because how roots respond to light varies by species. Some plant's react to light on their roots with a good degree of ambivalence, while others respond in a decidedly negative fashion. My guess, because this plant is so predisposed to formation of adventitious roots that it matters little or not at all. I do know though, that you'd be much better off if you potted the nodal cutting up in a grow medium rather than in water. Separate the cutting by cutting through the stem immediately below the node that supports the subject root and potting in a moist grow medium.. The roots that will form in water are very different than roots which form in a solid medium, and 'water roots' are very brittle and transition poorly to a solid medium.

Why is this one white and bulbous, though? Blanching inhibits production of chlorophyll and other sundry pigments, and blocks harmful rays of the sun that cause the periderm (outer skin) of other adventitious roots not deprived of light from dying and turning brown. This is (in part) how bark on trees is formed. The reason it is bulbous is because it is actively growing.

Al

Your cutting is a prime candidate for propagating sideways. If you have a node buried, an active exposed node, plus the growth tip, you could end up with 3 growing tips. Each node that takes root should (in theory, not always in practice) send out a new branch/stem/vine. If my goal was the fastest possible increase, I would put that in water a little deeper, so the subject node is also submerged. When both nodes have roots ready, plant it sideways with the roots nicely buried and the stem right at soil level. If your plant has studied the theory, you'll soon see the new stems coming from the rooted nodes.

Similarly, don't be anxious to have dangling over the edge if what you want is fullness, lots of vines. Nothing wrong with the single vine going around the room on hooks, but if that's not what you want, you have options. You can coil the vine around the soil surface. Not all nodes will take root no matter what you do, but a lot of them will, and send up new stems. You can put a small rock next to (on the stem, but not over the node part) promising looking nodes that don't want to stay down and touching the soil.

That is how this plant my boss brought to work for me to rescue has gone from a single vine with about 6 leaves to this: