“… arching their necks out of rotted tree stumps, sucking life out of death. … the forest eats itself and lives forever.” – Barbara Kingsolver The Poisonwood Bible
For those that follow this blog you will know that tree stumps appear regularly. Because they are still rooted in the ground rising damp tends to keep them moist and usually guarantees a good show of fungi. These photos were taken by Glenda Leete in Wallaceville, Upper Hutt.Glenda’s photos feature two leathery bracket fungi. But they also show the plasticity of form that bracket fungi have in the relationship to their substrate and their orientation to gravity. Ingold in his little book, which he calls an essay, on Dispersal in Fungi (1953).
Polyporus betulinus … produces its fruit-bodies on the trunks and limbs of dead trees … Gravity has a profound formative influence on the sporophore. The young fruit-body first appears erumpent as a small, undifferentiated spherical knob 2-3 cm. across. If this is on the main vertical trunk, it then grows out horizontally … to form a firm, more or less semi-circular structure, with a radius of 15-20 cm. and about 3 cm. thick, attached laterally to the trunk (Fig. 49A). If, however, the original spherical primordium is on the under side of an approximately horizontal branch, the fruit-body develops a roughly circular form with a central attachment to the tree (Fig. 49B). Fruit-bodies do not normally arise on the upper of a branch, but if a dead tree bearing primordia is felled, those on the recumbent trunk may continue their development. A primordium thus exposed on the upper surface of a fallen trunk grows out on one side only, more or less at right angles to the pull of gravity (Fig. 49C).It is, apparently, gravity also that determines the formation of the hymenial pores on the under surface of the fruit-body. These pores are at first very shallow, but throughout the life of the sporophore (8 months) they grow by means of an active zone around the mouth of each pore, so they gradually become longer. The direction of growth is conditioned by gravity so that the tubes produced are orientated precisely in the vertical direction. … In bracket polypores geotrophic growth achieves the desirable results of vertical hymenial surfaces, but if these, once formed, are slightly displaced from the vertical, there is no mechanism of readjustment in the pores. In Trametes gibbosa (Fig. 50), so common as a saprophyte on beech stumps, the morphogenesis of the sporophore is similar to that of Polyporus betulinus. Here the fruit-bodies arising on the more or less vertical surface of the trunk are of the bracket form, whilst those on the transversely cut surface of the stump are radially symmetrical with a broad central attachment.
These photos of Glenda’s shows tiers of brackets of Trametes versicolor growing on the vertical surface of the stump.While this photo of the cut surface shows the brackets growing from a central attachment as a simple rosette. If Trametes versicolor can have the appearance of a complex rosette if it colonises a narrow short stump as in the case of the photo, by Christine Harper, taken at Ohope. Just to complete this story some bracket fungi decompose the wood of dead trees and appear to sprout from the ground as a large rosette, in this case the size of a large cabbage. These photos where taken by Cary Moore in the Tararua Range. This could be Bondarzewia (berkeleyi ?) if it has distinctly amyloid and warted spores. Other possibilities are Ryvardenia campyla or Grifola. [see Jerry’s comment below re Bondarzewia kirkii] Glenda’s other fungus, Cerrena zonata, also formed tiers of brackets on the vertical surfaces of the stump. Ingold also talked about pores and there orientation. There is a marked difference between the two species on Glenda’s stump. Trametes versicolor has pores on its under surface and it produces spores on cells lining the pores. In contrast Cerrena zonata has spine, teeth and ridges on its under surface with the spore producing cells covering the surface of these. Glenda’s last photos shows night visitors on a foraging trip to the stump. PS: Peter Buchanan’s comment below reminded me of an illustration he published in the New Zealand Journal of Forestry Science in 1989. It showed all the forms that bracket type wood decay fungi can take.
Ingold CT 1953. Dispersal in Fungi, Oxford at the Clarendon Press.