Left Micrograph: The basal sphere is a flask-shaped ascocarp (= perithecium). The ascospores mature and are released inside the perithecium and are then squeezed out througth an opening at the top (ostiole) as a column (cirrhus) like toothpaste. The coiled hairs (setae) protect the ascospores from predation and at the same time function in the same way as the capillitium of a slime mould to support the spore mass and release the spores slowly over time for a more efficient dispersal. Chaetomium species are identified by the type of setae (straight, spiral, coiled, hooked etc.) and the size and shape of the ascospores (mostly dark and lemon-shaped).Right micrograph: shows cirrhus of ascospores and both dichotomous and simple (unbranched) setae.
Chaetomium species are strong cellulase produces and are associated with decay of paper, cardboard etc. They like to grow between the layers of sopping wet plywood (flooded homes!) and also they grow nicely inside those peat pots that the horticultural industry uses for plantlets. However, it has been shown that Chaetomium will have deleterious effects in the plants growing in such pots afrer colonization.
A propos the last comment, the photograph above of Chaetomium has an interesting story. Older readers may recall that many years ago you could go to your local nursery or supermarket and buy a narrow cellophane strip many metres long. There were an assortment of flower seeds embedded in the cellophane at intervals along its length. If you now unrolled this in a flower bed and covered it lightly with soil then you would have a dazzling array of choice blooms in a few weeks. Or so the claims stated. It didn't quite work out that way. Cellulose (glucose units in a chain) is a great source of energy for all kinds of fungi and bacteria including of course Chaetomium. Back to the story!
They were doing some tests on these strips in our horticultural department and a technician walked in to my lab one day with a piece of strip covered with fungus. Surprise! Surprise! Under the dissecting microscope it proved to be a Chaetomium. I made a quick mount (only took a few seconds) for the compund microscope and it was probably one of the best mounts of Chaetomium I've made before or since and that is the one you see above.
More important the Chaetomium was growing so well and producing the toxins I mentioned to the point where the seeds in the cellophane strip were not germinating. So there you have it, another million dollar idea down the tube!
Students : Why didn't they use plastic. It should take you a nanosecond to answer that one!