I don't know if this helps out at all in understanding these plants, but I'll just encourage people who are interested to watch the following video. According to the description for the video, footage was taken at Myburgh's Waterfall Ravine on Table Mountain, in South Africa.
Disa uniflora expedition - YouTube
There is no question,
Disa uniflora is a lithophyte from this video. The plants grow between rock crevices where the rocks stay consistently moist. When I say rock, I mean boulders in some cases. It is moist enough for a ton of ferns to grow there.
As evidenced in this video, they are not growing in sitting pools of water. The water is constantly dripping down the rocks and splashing along the surfaces of the rocks.
I can only make an assumption about the following claim because the person shooting the video did not bring a meter to measure humidity nor a thermometer, but it can be pretty safe to assume that due to the large amount of moisture around that area and the large winds, that the microclimate is cool and humid.
I think it solidifies my thought that the problem with Disas is not fungal, it is aeration of the root zone. Temperature may also not be a terribly big issue either, (although, they do have their limits). It may be that they may like lots of oxygenation around the roots.
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