I have had very poor success with apple seed kept dry over winter and soaked and frozen in the spring. My method is to plant in the fall. I have had very good success with planting the cores, or the pomace fresh from the cider press, covering not more than one inch deep.
The Woody Plant Seed Manual (2008)
As an alternative to macerating the fruits and subsequently storing the seeds, fermenting freshly collected, undried fruits of western mayhaw for 4 or 8 days yielded 93% germination. However, fermentation periods > 8 days adversely affected seed germination (Baker 1991). Most other reports stated that acid scarification and/or cold stratification are obligatory to enhance seed germination. Fermentation treatments may prove extremely beneficial in reducing the time required to produce seedlings of hawthorns. However, further research on a wide range of hawthorns is needed before making general conclusions about the usefulness of such treatments.
Seed Germination Data Sheet
6. The Lily Family (Liliaceae)
Seed can be collected by hand mostly from December to January. Capsular species release seed readily when dry. (Care needs to be taken with fleshy fruited species as the fruit can rot through paper collection bags). The fleshy fruit can then be soaked in water for several days until fermentation occurs. This may promote germination (except for Dianella tasmanica and D. longifolia) and enables the seed to be easily cleaned. Cleaning can be carried out by washing the fermented mixture through a sieve. In addition, Dianella revoluta may also respond to smoke treatment.
Nerson: Seed Production and Germinability of Cucurbit Crops (2007)
In most cucurbit seed production systems, seed fermentation in the juicy endocarp and mesocarp tissues of the fruits is the first step after fruit cutting and is employed for up to four days. Longer fermentation of cucumber seeds can decrease germination percentage and germination rate (Nienhuis and Lower 1981). This procedure not only facilitates the seed separation from the surrounding tissues, but also may results in increased seed nutrition value (Achinewhu and Ryley 1986) and seed germination (Harrington 1959). The relationship between fruit age at harvest and fermentation was investigated in most cultivated cucurbits (Edwards et al. 1986; Nerson 1991), and variable responses were recorded for different species. Generally, germination of fully-mature seeds is not affected by fermentation. Immature seeds of cucumber, melon and watermelon had a better germination, whereas the germination of immature squash seeds decreased after fermentation.
Tomato Seeds Must be Fermented to Germinate
Many plant seeds can be saved simply by collecting them as they dry. Tomatoes take a bit more work. The tomato seeds are enclosed in a gel like sack that contains growth inhibitors, preventing the seeds from sprouting inside the tomato. The best way to remove this gel covering is to allow the fruits to rot and ferment. In nature this happens when the fruit falls off the plant. For seed savers, we're going to speed up the process.
Van Mons collected unripe pears, then allowed them to rot before planting the seeds.
Cook: Hybridizing (1907)
When perfectly ripe, bruise the heps, or seed balls, and put them in sand. They will soon rot, when you can wash the seed out and sow it at once. It will take from three to ten months for any to come up.
Simon: Rose seeds fermented in tomato pulp.
Tomato pulp experiment
Tomato pulp experiment... some results