As a devout exponent of the species, I am pleased to announce that D. hartmeyerorum can be reliably germinated and grown during the cool and smoggy season (that's winter, to you non-Southern Californians).
Here's a picture taken today. The plants are in a two inch pot filled with pure, fine (unwashed) sand, residing in a tray six inches under four fluorescent bulbs. The tray sits on a commercial heat mat that keeps the air at soil level between 75 and 80 degrees F. The humidity hovers between 30 and 50% which is the system's saving grace. I tried to grow some plants last winter in a terrarium heated by an aquarium heater, but the constant high humidity stunted their growth.
This picture is from early fall. The conditions were the same for this plant, with the exception of the heating mat which was not used.
If anyone has a different method for growing this species, I'd love to hear about it.