· 'Dry' seeds include beans, okra, peppers, basil and members of the Onion and Carrot Families. Cleaning dry seeds usually involves simply drying and crumbling the pods or husks, then screening or 'winnowing' the seeds to separate them from the chaff (see Cleaning Dry Seeds).
· 'Wet' seeds are found in such plants as tomatoes, eggplants and many squashes. Cleaning wet seeds requires washing to clean the seeds and to separate them from the surrounding pulp (see Cleaning Wet Seeds).
· In addition, in some cases wet seeds (such as tomatoes) are best fermented for several days to remove germination-inhibiting substances from the seed coats (see Fermenting Seeds). Fermenting can also help such seeds as members of the Squash family by killing molds, mildews and other disease organisms that may be present on the seeds after growing.
Some families (such as the Cucumber family) include some plants that produce wet seeds (e.g., squashes and melons) and others that produce dry seeds (e.g., luffa and hard gourds). See Seed Saving Instructions for Common Vegetables for details on whether a plant makes dry or wet seeds, and whether its seeds must be fermented before cleaning and drying.
The above information comes from the following site:
Please be sure to go there for more detailed information on specific plants.