"Very Strange Conidia": Phragmotrichum thornhilliae

Phragmotrichum chailletii appears on spruce cones in early spring.

Here’s a not-terribly-exciting-looking little ascomycete that—if you live in northern areas of Europe or North America—you’ve probably stepped on in the woods without even knowing it. Phragmotrichum chailletii forms tiny (0.5-1 mm) black pustules, or perithecia, that erupt from the upper surface of the scales of fallen spruce cones. It frequently grows in dense numbers on the scales, though the ones I’ve found have always been scattered. I’ve found it two years in a row, both times very close to the same date, once on April 21, and once on April 24. It seems to like snowmelt moisture and cold temperatures.

Phragmotrichum chailletii is little studied, so there’s not much known about it other than that it’s apparently not a pathogen of spruce trees since it’s only found on fallen spruce cones, usually in early to late spring. It also only produces conidia, or asexual spores; a teleomorph, or "perfect" form of this fungus that produces sexual spores, is unknown. 

Phragmotrichum chailletii conidia

These conidia are what’s really fun about P. chailletii. In the original description (Kunze & Schmidt, 1923 - see reference below), the shape and structure of these conidia are described as "very strange" with no known analogy in mycology. 

The conidia develop in chains.

First off, they’re quite large—25-45 µm—which makes them photogenic. They’re brown and and multi-septate—“mûriforme” in French, or shaped like a blackberry. They’re produced in chains, that, when you’re lucky, show the progression of development from amorphous, non-septate tubes, to single septate, to double, and so on, until to they’re fully developed multi-septate “blackberries.” It gives me joy to look at them, as if I’m looking at a long-lost M. C. Escher print.

Conidia are released from the fruiting body of Phragmotrichum
chailletii when it splits open. (click to enlarge)

This is a view that reminded me of M.C. Escher's work.
I almost expected to see lizards.

References

Original description (in German): Kunze & J.C. Schmidt 1823, Mykol. Hefte 2: 84, t. 2:4

This paper offers a key to four Phragmotrichum species: B. Sutton, D.K. Sandhu, Phragmotrichum pini (W.B. Cooke), Transactions British Mycological Society, 52 (I), 67-71 (1969)