Past its Use-by Date .....

If you have ever gone away on holiday and forgot that you left some cheese in the cheese dish, then ....

..... this will be a familiar sight when you return home. This slab of Cheddar has become .........

...... a battleground for fungal colonies ............

....... that jostle for supremacy when the colonies collide, and in doing so create a rather attractive, furry abstract design.

Once the mould has smothered the cheese surface it's time to reproduce ....

..... via stalked sporangia ......

.... that resemble little white pom-poms...

.... each of which releases .......

... vast numbers of these minute conidiospores, each just a few thousands of a millimetre in diameter.

Fungal Artillary

Most fungi tend to be associated with autumn but there are a number of perennial species that can be found at any time of year, including this one - variously known as King Alfred's cakes, cramp balls or Daldinia concentrica. The first name refers to King Alfred's culinary accident while hiding from marauding Danes in the humble abode of a cowherd; the second refers to the folklore that carrying this fungus around in your pocket stops you getting cramp in the legs (doesn't work for me); the last refers to .....

.... the concentric rings of annual growth that you can see if you cut the fungus open.

The blackened surface of the fungus is covered with scores of these 'pimples', each with a pore in the centre. Each leads to a chamber below, packed with tubular flask-shaped fungal hyphae called asci, each with eight ascospores inside. Cut one of these chambers (in mycological parlance a perithecium) open and this....

... is what you see under the microscope - rows or rugby-ball shaped spores, seen here at around x100 magnification and ....

.... here at x400 magnification. In spring each ascus of eight ascospores elongates in turn, until its tip protrudes from the pore in one of those surface 'pimples', like a cannon protruding from the gun port of a man 'o war. Pressure builds inside the ascus until it ruptures and fires out its salvo of spores. Then it withers, another elongates to take its place and the discharge is repeated. This can go on for 6-7 weeks before all the asci have fired their broadsides, with most of the spore discharge taking place at night. You can watch this by placing the fungus in a light beam in a warm room - if you've got sharp eyes you can see what look like little puffs of smoke all over the surface - the fungus firing its silent broadsides. In England Daldinia concentrica mostly grows on ash trees but in Scotland it also grows on birch.

The Magic of Mushrooms

These are the radiating gills of the toadstool known as weeping widow Lacrymaria velutina. For more about this toadstool, visit http://cabinetofcuriosities-greenfingers.blogspot.com/2009/10/weeping-widow.html

The surface layer of the gills, known as the hymenium, produces thousands of spores, and for these to be successfully released into the airstream the gills must always be vertically aligned, so they are very sensitive to the force of gravity and quickly realign themselves if the stipe of the toadstool bends away from the vertical and tilts the cap.

Here, at a microscope magnification of x40 you can see the spores lining the surface of the gills....

...and here, at a magnification of x100 you can see that each is shaped like a small brownish-black lemon..

The spores are formed in groups of 4 on a cell called a basidium, attached to it by short stalks, seen here at a magnification of x400 under the microscope....

... and these appear to be two basidia where the spores are beginning to form. When they're mature and drop off they'll fall vertically down the gaps between those parallel, perfectly vertical gills and will be wafted away in the airstream

If you cut off a toadstool cap, turn it gill side down on a piece of paper of contrasting colour to the spores and leave it in a warm room where there are no draughts for a couple of hours, the falling spores will produce a beautiful spore print.....

...like this

Well-Travelled Fungus

Groundsel cluster cup fungus, looking like minute tarts, on an infected groundsel leaf surface. The spores are produced in vast numbers in the centre of each cup. Each cluster cup is about as large as a full stop (period) on your monitor screen. A minute larva of a fly is crawling across the leaf surface, just to the right of the open cups, and may have been feeding on the fungal spores. In the bottom right corner (below) cluster cups are just forcing their way to the leaf surface, ready to open.

Cluster cups erupting from an infected, swollen stem. Infected stems often develop purple pigmentation and become distorted. Heavy infestations can be fatal.

 

Above: A vertical section through a cluster cup on a leaf surface, x100, showing the chains of spores that are formed in the centre of each cup.  

Below: Although apparently heathy, this plant is infected with the fungus, just visible on the surface of the bottom leaf on the left in the middle of the picture 

Take a look at the weed groundsel Senecio vulgaris stems and leaves in autumn and you’ll often find that they’re swollen and distorted, with a patches of a yellow fungus erupting from their surface. The infection is a fungus called groundsel clustercup Puccinia lagonophorae, which has an interesting history, having travelled more than half-way round the world since the mid-20th. century. Migratory people tend to take weeds, as well as their crops, with them and groundsel was accidentally taken to Australia by early settlers from Britain, where it became infected with this fungus which is native to Australia. Some clustercup-infected groundsel made the return journey and the fungus arrived in Europe in 1961, where it has been spreading ever since. More recently, within the last decade, the fungus crossed the Atlantic and has begun infecting groundsel that had been taken there by early European settlers. The Americans are not altogether sorry that the fungus has arrived, because it weakens groundsel and might offer a means of biological control of this invasive weed. In the photographs you can see the flower-like spore cups, called aecia, that produce the infective golden yellow spores. In the vertical section through one of these cups (second photo from bottom) you can see the chains of spores budding off from the fungal hyphae.

Oak Leaves Under Attack

Several tree species - most notably oaks - put on a new flush of growth in summer, sending out shoots with fresh green foliage (bottom photograph) to supplement the older leaves of spring that have suffered from insect attack and general wear-and-tear. The new shoots are known as Lammas growth, because they’re well developed by the ancient Celtic harvest festival of Lammas day - 1st. August. Lammas growth is most prominent in younger trees during this 'second spring', but sometimes the freshness of this new foliage doesn’t last very long. Take a look at the new shoots and you’ll find that many will be distorted and coated with a greyish-white powder (second photo from bottom). This is the parasitic oak powdery mildew Erysiphe alphitoides that thrives in the warm, humid weather that we’ve been experiencing lately. Under the microscope you can see a mass of transparent fungal hyphae covering the leaf surface (third image from bottom) visible in the microscope photo (x400) in the clear areas between the blocks of green tissue. The hyphae draw their nutrition from the delicate new leaf tissue and send up short aerial hyphae that bud-off powdery spores (fourth and top images, x100 and x400 respectively), that blow away in the wind and infect another leaf.

Every Fly’s Nightmare

I found about a dozen dead flies like this one, head down, tongues extended, clinging to the flower heads of meadow foxtail grass. They’ve been killed by a fungus called Entomophthora muscae, that invades the insect through one of the joints in its external skeleton and attacks its nervous system, modifying its behaviour so that it climbs to the top of grass stems and clings on while the fungus digests its internal organs. Fully fed, the fungus then erupts through the joints in its victim's body, covering the dead fly's abdomen with a felty mass of fungal material that produces gelatinous-coated spores that cling to the next hapless fly that arrives in the scene, sealing its fate. The spores can be fired some distance from the corpse, so they also coat surrounding vegetation. The bottom photograph shows the highly magnified (x200) sticky spores and the next one up shows a mass of sticky spores adhering to a hair on the leg of the corpse (x100). It's Hammer House of Horrors stuff.