The whole plant is hairy on the Dresslerellas. In general, hairs on plants help to reflect light away from them, allowing the plants' internal temperatures to stay lower than that of the surrounding air. From the information I was able to find, these are pretty temperature-tolerant plants, so it must work! They certainly are vigorous growers for Ecuagenera...
Hairs and red pigment on leaves are both common adaptations to high light - they're good examples of parallel evolution - you can see similar adaptations in many plant families in similar environments.