Working With Illustrated Genera Of Imperfect Fungi in Modern Practice
I ran into a culture I was trying to ID a few years back — isolate from soil, producing sparse white mycelium and what looked like simple phialides on short conidiophores. The culture wouldn't sporulate under any of the standard conditions I tried. I ended up flipping through the illustrated plates of Illustrated Genera Of Imperfect Fungi because the molecular data came back muddy, and I needed a morphological anchor. That book has been around since 1962 with subsequent editions, and it remains one of the few practical field references organized by conidial morphology rather than taxonomy. The original and revised editions cover imperfect fungi — meaning fungi known only in their asexual state, or anamorphs. It groups genera by how their asexual spores form and what they look like under the microscope. The basic organizational logic runs through acrosporic conidia, endospores, blastospores, chlamydospores, and various conidiogenous structures. Each genus gets a brief description, sometimes a line drawing or two, and references to the primary literature at the time. The main problem people hit when they open this book is that the genera aren't arranged phylogenetically. They're arranged morphologically, which means related species can end up on opposite pages, and some genera have been split or merged since the last edition. I learned this the hard way when I was looking for Phialophora type morphologies and found entries scattered across three different sections because the authors categorized them by lesion type on the host plant rather than by conidial structure alone.
How to Use It Without Wasting Three Hours
Start with the conidiogenous system. That's the structure that produces the spores, not the spores themselves. Most identification keys in this book route you through conidiophore architecture first — whether the conidiogenous cells are integrated into the mycelium, forming discrete stalks, or arising from specialized structures like monilethric hyphae. Get that wrong and every subsequent key couplet leads you further from the right answer. Mount your specimen in lactophenol cotton blue and take the time to check for septation patterns on the conidiophores. This took me about 45 minutes on a typical slide prep, including figuring out that my stain had dried out halfway through because the bottle cap wasn't sealed well. Fresh mounts make a visible difference under higher magnification, especially when you're trying to distinguish Alternaria from Ulocladium — which comes down almost entirely to the size and septation of the conidia, not the shape. The book references are dated but not useless. When it points you to a paper from 1978 describing a genus revision, that paper often still holds up. The taxonomy may have shifted, but the morphological descriptions in those older papers tend to be more detailed than what appears in modern abstracts. I keep a folder of scanned references that trace back to the Illustrated Genera citations, and roughly half of them are still valid for practical identification purposes.
The Parts That Don't Translate Well
Some genera in the book simply don't have clear diagnostic features when you're looking at them fresh under a microscope. Cephalosporium type morphologies, for instance, overlap heavily with other hyphomycetes, and the illustrations in the text show clean, textbook specimens that rarely match what you see on an actual plate. I spent two weeks trying to nail down a Cephalosporium isolate before realizing the conidiogenous cells were actually branching in a way that matched Acremonium instead. The book acknowledges this ambiguity in places but doesn't give you a practical path forward when two genera look identical in your hands. Another limitation is that the book only covers the anamorph state. If your organism produces a sexual stage, the classification it points you toward may be entirely wrong because teleomorphic reclassification has moved many genera into Ascomycota or Basidiomycota frameworks. I encountered this repeatedly with cultures that initially keyed out as one genus in the Illustrated Genera but then produced perithecia on Potato Dextrose Agar, revealing a completely different taxonomy underneath. The book won't help you with that transition, and you'll need a secondary reference like Dematiaceous Hyphomycetes by Evans or the more recent molecular phylogenetic revisions to resolve it.
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What to Do When the Book Falls Short
When morphology alone doesn't resolve the ID, sequencing the ITS region or the TEF-1alpha locus gets you further than flipping through more plates. This usually takes about a week from culture to result if you're outsourcing, or three to four days if you're doing it in-house. The morphological key from Illustrated Genera still serves as a useful starting point for narrowing down which genera to consider before you commit to sequencing, but I'd treat it as a first pass rather than a definitive answer. The book itself is available through various mycological societies and used book markets. New copies are occasionally listed through academic publishers or specialized mycology suppliers. There is no single official digital version that I'm aware of, though some institutions have scanned portions for internal use. If you're working with this regularly, buying a used copy is more practical than trying to source chapter scans, since you'll be consulting it frequently enough that the physical book pays for itself within a few months of lab work.
