why are the begonia corms i planted in containers not showing when those which i planted at the same time i my garden borders are 1 to 6 inches above ground???

Have you had a poke around in the soil to see if they have rotted off? Sometimes they get over watered in a container. Or maybe they were too dry?

mine also had no signs of life and on closer inspection they had rotted.i have a good excuse now to buy some more.

water from below until they sprout.

Like Voluneteer says, it is probably worth doing an excavation of one just to examine to find out what is going on. Do it gently. If you find it is still alive, you can settle it back.