Trout makes a good point. About a month ago, I unpotted a bunch of random D. Capensis seedlings and reused the pot/media which had a little bit of moss growing in it to sow some gemmae (not recommended, but I was low on soil at the time and just decided to wing it, oh well....). Some of the gemmae fell on the moss and as such, did not sprout, while the ones exposed fully to the untouched/free media sprouted within a couple of days. After about a week and a half of no activity for a few (and after getting some more peat in the mail), I moved the unsprouted gemmae to some fresh media not really expecting any results, and they immediately took off and are doing fine. It may not hurt to try to push them into the moist media just a touch more, or to really make sure the top of the media is moist enough (sometimes the tray method doesn't allow quite enough moisture to the top, depending on what your environmental conditions are).