isn't there a plant or tree in Australia whose seeds only open in the heat of a fire? They require fire to germinate.

Greetings Sinsull,
I don't think there has been specific mention of this in this thread, so here goes.

It's not usually the seeds that open but the fruits, but that's probably just the pedantic botanist in me. Many Oz plants have woody fruits; some insulate the seeds within from short exposure to heat. Some eucalypts have capsules (the technical term for their fruits) that have pedicels (the technical term for the stalks attaching the capsules to the rest of the tree) that burn through in a flame, allowing the capsule to drop onto the ground where, perchance, the fire's heat passes over without the heat penetrating the capsule's insulation. Most eucalypt capsules open as a result of it drying out and this happens after the fire front has gone. Winds may break small branch tips off eucalypts and, if they're carrying fruits at the time, the capsules later dry out and release their seeds.

Some seeds of eucalypts and wattles (Acacias) have tiny little sweet bits on the end so that ants seek them out and carry them underground, where they are better protected from heat. Eucalypt seeds may eventually decompose in the soil's moisture or may germinate after a period but be unable to establish because of the dense shading of fully established vegetation. Most wattle seeds have a seriously protective coat that resists such decomposition for many decades and must be breached before the seeds can germinate. The usual method of breaching is the high temperature of a fire, which is why wattles can be the among first to appear after a fire. Mountain ash seeds might be slower off the mark but will outpace the wattles and quickly become taller than the wattles, gradually inhibiting the species that require full sun and allowing only those species that can tolerate shading to subsequently become established. That's the story behind the Prickly Moses at the Prom.

The eucalypts belong to the Myrtaceae family and others in this family (tea trees, paperbarks and bottlebrushes, eg) all have similar woody capsules that, to some extent, resist heat and release their seeds by drying out.

Probably the most spectacular of the other Oz plants with woody fruits are the Proteaceae family, particularly Banksias, Grevilleas and Hakeas. Their fruits (technically follicles) mostly will resist fire, which then starts a slow process by which the follicle gradually opens, releasing the seeds (two per follicle) onto a cool ash bed that has possibly already had some rain on it. These species specialise in growing on soils with low phosphorus content (too much, as in normal fertiliser) will kill them. Another group (and this is relatively new research) require their fruits to be exposed to wood smoke before their seeds can germinate; there is a chemical in the smoke that dissolves into part of the fruit and triggers germination. This may be widespread among Oz native plants; I only know that it affects Wax flowers (Eriostemon) species in particular.

And no, apart from my thesis I haven't written any books; it was an offputting experience. But getting others enthused about the things that enthuse me has been the story of my life, I suppose, so I've spent a lot of time teaching and this has led to various small bits of writing. And, in the case of this thread, I've come to suspect that concentrating on the material that I have posted has kept me "up" in the face of so much that could lead me "down". So I owe y'all some thanks.

Cheers, Rowan