I like to try to grow flowers from seed for example shasta daisys and anyway I get them to sprout and they grow till about 1/2 an inch and then they shrivel up at the bottom of the stem and die. I will use a bag and make a green house affect and it seem when I take the bag off it dies. I keep it well watered after I take the bag off so it doesn't dry out.what is the problem.

It might be a fungus called damping off that sometimes strikes new seedlings. Hereis a web site about the prevention and control:

http://gardenhobbies.com/howtogrow/dampingoff.html

This web site also has lots of other good garden information.

Be sure not to over water as the bag holds in most of the moisture your seedlings need...a heat source to the bottom of your plants is a plus and a florescent light about 3" away from the plants should do the trick.