what is the difference?

So I know there is a difference between a pappus of scales and a pappus of capillary bristles. But on some species it is really hard to tell! On Monday I have a test in my plant systematics class. I'm not too worried about it, except for the Asteraceae. It is hard for me to tell if the receptacle is naked or chaffy, and if the pappus is scaly or bristly! I hope we don't get many different kinds of Asteraceae.
Plant systematics makes me dream about obscure plant words and names (like Solidago missouriensis or Sonchus uliginosis). Repeating these thing over and over again does not really facilitate memorization of what the plants actually look like. You just know some funny words.
Here is our class website, where Dr. Lavin posts pictures of all of the plants we've so far studied. Gorgeous!