American Scientist

To the Editors:

In reading the article "Leaves, Flowers and Garbage Bags: Making Waves" by Eran Sharon, Michael Marder and Harry L. Swinney (May–June), we were struck by the similarities of the organisms in their article to the undulate growth forms of fungi, both in nature and when isolated into pure culture.

Field biologists will recognize the wavy-edged pileus of Clitocybe phyllophila (Basidiomycetes: Agaricales) and the ruffled margins and color changes used to identify the turkey tail fungus, Trametes versicolor (Basidiomycetes: Aphyllophorales). Plant pathogens such as wood-rotting fungi including Grifola frondosa and Laetiporus sulphureus (Basidiomycetes: Aphyllophorales), as well as the conifer root-rot disease caused by Rhizina undulata (Ascomycetes: Pezizales), also exhibit these forms.

When grown in pure culture and producing essentially one-dimensional colonies, numerous fungi exhibit characteristically wavy margins; an example is the mycelium of the dogwood anthracnose fungus, Discula destructiva (Fungi Imperfecti: Coelomycetes). Sometimes "waviness" or, in a mycological sense, undate or undulate growth is more noticeable as sporocarps of macrofungi reach maturity, such as in Cantharellus cibarius (Basidiomycetes: Aphyllophorales).

Waviness, twists and convolutions apparently allow the fungi to grow to a larger size, as in the large sporocarps of cauliflower mushroom Sparassis crispa (Basidiomycetes: Aphyllophorales). These wavy growth forms also facilitate identification. At the macroscopic level, therefore, the phenomenon of hyphal-tip growth appears analogous to the meristematic growth forms discussed in the article, despite the fungal habit typically being explained as a preferential growth response to nutritional gradients.

Limiting their study to autotrophic lichens (dual organisms consisting of algae and fungi) may reveal only "half the picture" because fungal hyphae of successful saprobes, ectomycorrhizal symbionts, plant pathogens, and endophytes may exhibit the same phenomenon at the microscopic level. Perhaps waviness should be of greater scientific significance than a morphological feature within fungal phylogenies. We wonder if there is greater consilience among fungi, fractals and frayed configurations than the authors' first thoughts on flowers, lichens and aquatic animals.

Eileen M. Sutker
Scott C. Redlin
U.S. Department of Agriculture
Raleigh, North Carolina