I am an amateur seeking to identify every living thing in his garden.
I have a galvanised-metal incinerator bin in my garden, the lid of which can see be seen in photo 1 (I am sure you will be fascinated to see it!). Said lid has, for some months, been lying untouched at one edge of my lawn (at (1.2,1.9) - see here). On a whim I lifted it recently expecting I might discover a beetle or two to act as raw material for this blog. I was surprised and delighted however, to discover the entity shown in photo 2 (click on it to enlarge).
I feel fairly confident in identifying my mushroom as the Yellow Morel (Morchella esculenta - see Rogers mushrooms for more photos), an edible mushroom highly prized by chefs (though it is worth adding that morels should not be eaten raw and worse, the superficially similar-looking False morel (Gyromitra esculenta) can be deadly poisonous).
It is probably no coincidence to find a morel in close proximity to my garden incinerator since morels are often associated with burnt ground. According to my copy of Fungi (B. Spooner & P. Roberts, publ. Collins New Naturalist and refs. therein) in times past "the peasants...of germany...set fire to forests in order to obtain these fungi".
Why the curious shape? The short answer is that if, like fungi, you are in the business of reproducing by allowing air currents to carry away your spores, it pays to maximise the surface area you present to the passing breeze; Hence the many pits and grooves on the morel.
A more in-depth answer (of sorts) is as follows: The fungi are a huge kingdom of perhaps nine-million (!) species outnumbering vascular plants by perhaps six-to-one. People who study fungi (mycologists) break this kingdom down into two great divisions ('phyla'), the basidiomycota and the ascomycota. The majority of the more familiar mushrooms and toadstools (i.e. "caps-on-stalks with gills underneath"), including most edible mushrooms, fall in the basidiomycota. The ascomycota on the other hand are generally less familiar, although both morels and truffles fall in this phylum. Unlike the basidiomycota with their "gills", the ascomycota typically try to maximise their surface area by presenting concave "cups" to the air. The morel's complex surface is nature's attempt to pack lots of 'cups' side-by-side.
Under the microscope there is a more fundamental difference between basidio- and ascomycota: Whilst the basidiomycota produce 'free' spores on the spaghetti-like hyphae (see a previous posting) that make up the fungus (like apples on the branches of a tree), the ascomycota on the other hand produce spores inside special hollow tubes called 'asci' (like peas in a pod). The asci eventually rupture to liberate the spore. I gathered a small piece of my morel and at x1000 magnification (1 small graticule division = 1um, see photo 3, click to enlarge) the asci are clearly visible. One touches the numbers '0' and '1' on the graticule. A free spore is also visible at '6' .
Finally, I learn from the book above that the world market for morels is worth more than one-billion pounds per annum. "Lot 1 ladies and gentlemen, a genuine Oxfordshire yellow morel. Shall we start the bidding at one-hundred guineas...?"
As you will see from the comments, those familar with fungi are appreciative of my good fortune in finding a morel. I cannot resist adding a quote therefore, that was sent to me by an acquaintance. I am informed it is taken from It's My Delight by Brian Vesey-FitzGerald published in 1947 "Hares....are also very fond of fungi, especially the mushrooms, the various puff-balls, Scotch-Bonnets, Shaggy Ink Caps, and several others. They will invade gardens to get at morels which often grow in borders" [my emphasis]. Rather sad to think of what has been lost.