Identifying Scented Geraniums Grown from Seed

I purchased a package of mixed scented geranium seed last year. I had five plants thrive. My question is: how do I tell one from another another? I can tell that one is citronella by its strong scent, but not the others.

Because the supply of scented geranium seeds (Pelargonium spp.) is unstable, we provide a mix of whatever species we can get. In past years that might include some, but not all, of peppermint (P. tomentosum), apple (P. odoratissimum), lemon, coconut (P. grossulariodes) and balm-scented (P. vitifolium). From the scents alone you should be able to sort out some of the plants, but because the Pelargoniums are likely to cross- pollinate, don't be surprised if you find something new that no one has grown before.
A good book is Jim Becker and Faye Brawner's "Scented Geraniums: Knowing, Growing and Enjoying Scented Geraniums" available from Richters. Almost 100 varieties are discussed including all of the species likely to be found in our seed mix.