This looks to be some kind of peppergrass, and a search on Dogpile I did turned up one site for a dried flower supplier that that identified its "Petticoat Lace" as a "sm peppergrass." The genus is lepidium -- it's a brassica, a member of the mustard family. They're fairly common spring wildflowers/weeds that you usually find in old hayfields, pastures and other open areas. There are a lot of species and they have a lot of similarities when they're dried. You could do a Google image search on peppergrass to see likely candidates (before drying). You can also search for "lepidium" on the USDA Plants database, but be sure to select the "scientific name" search option. Using the "common name" option and searching for "pepper grass" gets no results for some reason. For my money, L. virginicum seems to be a good possibility, but I really can't tell.

Here is a link that might be useful: USDA Plants Database