There are several mechanical ways of sorting out good from bad seed, principally based on the differential in weight between a good, full fertile seed, and the lighter, hollow infertile seed (Including those parasitised by insects). Simple winnowing often works wonders, and vibration combined with gentle blowing usually separates out the lighter from the heavier fraction quite well. For larger, robust seeds such as Ipomoea, it can be worth trying a flotation technique. Get a bowl of water and put the seeds in it: the heavy ones will sink but lighter ones float and can be poured away. Occasionally surface tension will hold up good seed, but a bit of a swill-around soon overcomes this. If you're not planning on sowing the seed at once it is important to get the seed dry again as quickly as possible: I use kitchen paper towelling and just leave them to air dry in a warmish room - it takes a couple of hours. Then they can be packeted and stored in the usual way. John Grimshaw Dr John M. Grimshaw Garden Manager, Colesbourne Gardens Sycamore Cottage Colesbourne Nr Cheltenham Gloucestershire GL53 9NP Website: http://www.colesbournegardens.org.uk/