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Provisional World Key to Species Closely Related to Amanita hemibapha with Notes on the “Slender Caesar’s Mushrooms” of Eastern North America

Rodham E. Tulloss, P. O. Box 57, Roosevelt, NJ 08555-0057, USA

Revision of (Tulloss. 1998).
Most recent change: April 22, 2007

Background tile: Amanita garabitoana on world map showing approximate distribution of Amanita stirps Hemibapha as currently known.

Amanita sp. CR6 Photo: R. E. Tulloss

In 1986 [Boston Mycol. Club Bull. 41(3): 10-13], I wrote a little summary of what was known about Amanita hemibapha (Berk. & Broome) Sacc. and its subspecies. I reported then that the North American Caesar's mushroom should probably be called A. hemibapha. I have begun to study this group of amanitas in greater detail, and thought it was time for an update. A More Conservative Approach It seems that a more conservative attitude may be appropriate. Until a better understanding of all the involved taxa has been obtained, I now think it is best to treat our red “Caesar's mushroom” as a distinct species and to use the existing name for that, North American entity—Amanita jacksonii Pomerleau.

To give the reader a feeling for the number of North American taxa in the group of species similar to A. hemibapha (let's call it “stirps Hemibapha”), a provisional key to the group has been prepared. It is nearly certain that there are more taxa in the world than are accounted for in this key; for apparently new species of “stirps Hemibapha” seem to be reported on a regular basis by my correspondents and in the literature.

This key is restricted (as much as possible given current knowledge) to taxa apparently more related to A. hemibapha (described from Sri Lanka) than to the true A. caesarea (Scop.:Fr.) Pers. of Europe. The latter taxon has a subhymenium up to five inflated cells thick—as opposed to the one to three cell subhymenium thickness that, at present, I take to define “stirps Hemibapha.” A number of taxa included in this key have not yet been reviewed by me; and, undoubtedly there are errors. In addition to A. caesarea and its white variety, at least four additional, Mexican taxa with the thicker type of subhymenium have been omitted from the key in keeping with the delimitation of its scope. The omitted Mexican species include (1) an orange-capped species common in markets of the central volcanic region, Amanita basii Guzmán & Ramírez-Guillén; (2) A. laurae Guzmán & Ramírez-Guillén; (3) A. yema Guzmán & Ramírez-Guillén; and (4) a white species eaten by the Mountain Pima in the region of Nabogame, Chihuahua [Laferrière, 1991; Laferrière and Gilbertson, 1992]. The overall number of taxa with the thicker subhymenium similar to that of A. caesarea is not known.

There is a third group of robust, often colorful taxa of Amanita section Vaginatae that often have an annulate stipe and share many characters with the taxa in “stirps Hemibapha” and “stirps Caesarea.” These are taxa with subhymenia not dominated by inflated cells -- tentatively called stirps Calyptroderma. Amanita calyptroderma G. F. Atk. & Ballen [=A. lanei (Murrill) Sacc. & Trotter =A. calyptrata Peck non Lam.) is one species of this stirps that is common in the western U.S.A.; another is one of the undescribed entities known as “A. caesarea” in the SW states of the U.S.A. The number of taxa in this third group is not known.

The “slender Caesar's mushrooms” of the New World

How many members of “stirps Hemibapha” do we have in North and Central America? What are their ranges? We may not have the plenitude of taxa in this group that can be boasted by southeast Asia; but, nevertheless, the New World members of “stirps Hemibapha” form a strikingly beautiful part of our mycological patrimony. Let's indulge in some mycological “hemisphere chauvinism” for a few moments.

We are all familiar with the beautiful red Caesar's mushroom depicted in North American mushroom field guides. Mushroom book authors covering the fungi of eastern Canada, the eastern U.S.A., and eastern and central Mexico often include a striking illustration of A. jacksonii in their books. It is less well known that in this same region (and extending southward at least to Costa Rica) there occur a number of closely related species of “stirps Hemibapha” ranging from drab to showy in coloration and, in size, from the length of my index finger to two-thirds the length of my forearm. Among the largest of the species are A. arkansana Rosen (known from the southeastern U.S.A.) and Amanita sp. CR6, a beautiful species with an orange-brown cap and hints of olive in the stipe decorations, that will be described in the near future based on material from Honduras and Costa Rica.

There are several collections of a member of the stirps with a cap having a brownish disc and buffy cream margin. These mushrooms are referable to Amanita murrilliana Singer (see key, below). This entity gets the prize for the most retiring and unobtrusive coloring among known Western Hemisphere members of the stirps. It is also an oddity in that it is the only member of the stirps in which the base of the stipe is usually attached to the universal veil on its sides as well as at its very bottom.

Many mushroomers familiar with the oak-beech-hickory woods of the eastern half of the U.S. will have seen a small “caesarea” with the stature of A. jacksonii, but with a yellow to orange-brown cap instead of a red one. This is not simply a faded jacksonii, but a distinct species called Amanita sp. 16 in the key below. It is this species that I believe was illustrated by Peck's correspondent Mary Banning in one of her beautiful and idiosyncratic watercolors labeled “Agaricus caesareus.” It would be most appropriate to name the species for Miss Banning, and I hope to do so soon.

There is at least one more species in the stirps that I know only from collections brought to me from Florida by Aaron Norarevian (Glen Oaks, New York). This species has a yellow cap with a red umbo and is known only from sandy coastal plain habitat.

Will we find more of these interesting and colorful species in North and Central America? Quite possibly. There remains a considerable area that has not been explored by mycologists and ethnomycologists. If such species exist, they may be a part of the diet of indigenous peoples and could be first noted by scientists in markets. And how will we know if we have something new? We need a key to what is known. The following might serve as a rough start.

A key

The following key is very rough and is too frequently based on pileus coloration without regard to other macroscopic and microscopic characters. I hope this problem will be relieved in time.

Some more caveats: There are four groups of names or provisional names that may actually represent a single taxon each. These are to be found at key choices numbers 6, 7, 27, and 28. Hence, between 30 and 35 taxa are represented in this key. Additional material from India and Thailand (representing as many 5 additional taxa) has been seen by me, but not reviewed microscopically. In addition, there is work underway in several quarters that will undoubtedly clarify species concepts involved and the relations among the taxa. Z. L. Yang has just completed a thoroughly fascinating, detailed account of the amanitas of southwestern China in a Ph.D. thesis at Tübingen University. A number of relevant taxa are treated in this work (Yang, 1997). Dr. Alec Wood (Oatley, New South Wales, Australia) has recently published a paper describing several additional taxa close to A. egregia D. A. Reid (see below) from eastern Australia. In other words, this key will require revision soon.

Accurate knowledge of geographic ranges of the included taxa is not available; I have listed what information on range is known to me. A hollow bullet ( ° ) before a name indicates that I have personally reviewed material and that the spore measurements are mine.

In the sets of spore data, bold face Q is the average of the length/width ratios of all measured spores for a single specimen. When more than one specimen has been examined, a range of values of Q is presented. Q gives a feeling for the shape of the spores (Bas, 1969) observed as follows: 1.0 - 1.05, globose; 1.05 -1.15, subglobose; 1.15 - 1.30, broadly ellipsoid; 1.30 - 1.60, ellipsoid; 1.60 - 2.0, elongate; 2.0 - 3.0, cylindric; > 3.0, bacilliform.

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Originally transcribed to HTML by Dr. Michael Kuo.
Maintained by R. E. Tulloss
Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 by Rodham E. Tulloss
Photograph and map copyright 1999 by Rodham E. Tulloss.