It can often be tricky to work out which way is "up" with bulbs, corms and tubers! I think of the trouble we've had in the past with certain Arisaema corms!
It's a while since O planted any of these Hermodactylus/ Iris so I can't remember which is the "right way up".
My advice for any time when you are not sure is to plant them sideways - in this case "flat" - be sure that the plant will know itself which direction to grow. It may take a year or so to settle down to flower, by the way - but I hope you will get flowers next year. Ours are growing quite happily in a sand bed in a glasshouse, they must be around two to three inches deep in the sand.
