对于外有硬壳的种子,试试用这个 - nail file
http://www.google.com/imgres?q=nail+file&um=1&hl=en&biw=1140&bih=505&tbm=isch&tbnid=CPm7EDFJLhmtuM:&imgrefurl=http://www.nail-art-ideas.info/2011/02/nail-file-2011/&docid=VTbHEW9V-N8ErM&imgurl=http://www.201bride.net/web%252520exclusives/Carry%252520Kit/nail-file-WEB.jpg&w=450&h=279&ei=QSdgT4_SE4eqiQKez72TDQ&zoom=1&iact=hc&vpx=815&vpy=31&dur=1287&hovh=177&hovw=285&tx=198&ty=102&sig=108984509146963378649&page=1&tbnh=127&tbnw=129&start=0&ndsp=14&ved=1t:429,r:6,s:0