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Trick or treat?

September 14, 2012

Do you remember my blog in May about a choice mushroom and its assassin look-alike? I really put an effort in being pedagogic there. As it turns out, the appearance of new life forms confuse the concepts of a monsoon gardener.

Right now, there is a handsome parasol mushroom making many fruitbodies in the Dokmai Garden monsoon woodland. It has the characteristics of both the previously treated mushrooms. Of course, if you find something that does not match a description of an edible mushroom, you should not eat it until you know what it is. No mushroom book is complete, there are always more mushrooms out there. My pleasure is to investigate and share knowledge. Open the previous blog in another window so that you can compare the pictures side by side:

To begin with, this new species makes fruitbodies in the shady woodland, not in the compost or the lawn like the other two (the edible parasol Macrolepiota procera and the vomit mushroom  Chlorophyllum molybdites). I checked all over Dokmai Garden, the other two are not out now, while this new mushroom is found at several places among the leaf litter under longan (Dimocarpus longan) and Dipterocarpus alatus.

Secondly, this new mushroom is emerging now in September, it was not found in May. These observations may not be characteristic, but future observations will show whether there are constant seasonal and ecological differences or not.

As to the morphological characteristics, the stipe does not have the dense conspicuous brown scales like the edible parasol mushroom (Macrolepiota procera). In that respect it may resemble the dangerous vomit mushroom (Chlorophyllum molybdites). However, the cap has tiny grain-like scales. In that respect it does not resemble any of the other species, which have large scales. The stipe is strikingly gracile, a feature we shall come back to. At the base is a more or less conspicuous bulb.

At a closer look, the stipe of a mature specimen has tiny brown scales, unlike both the edible parasol (large brown scales) and the poisonous vomit mushroom (no scales). When bruised it turned brownish red after a long time, a characteristic of the vomit mushroom but not of the parasol. The slenderness is illustrated by the fact the 34 cm tall specimen to the left in the top picture had a stipe which was only 10 mm broad above the bulbous base, and 8 mm broad under the ring.

The gills are white, which does not hint at the vomit mushroom with its green gills. The fragrance is appealing, mushroomy and spicy.

The spore print is white, not green as in the vomit mushroom.

The tiny grain-like scales hint at a species Julius Vincenz von Krombholz in Prague called Agaricus gracilentus in 1836. This physician made a hand-coloured book to teach other naturalists about edible and poisonous mushrooms. It was one of the first mushroom floras with colour illustrations and is still a wonderful piece of art. Later, German mycologist Meinhard Moser transferred the mushroom to the genus Macrolepiota.

According to Mycobank the valid (oldest) name is Macrolepiota mastoidea, a name (mastoideus) coined by the Swedish mycologist Elias Fries in 1821 and transferred to the Macrolepiota genus by the German  mycologist Rolf Singer in 1951.

Since all pictures of M. mastoidea I have seen on internet and in books depict mushroom caps with large scales, while the original description for Macrolepiota gracilenta emphasises small grain-like scales (like in this case), the two mushrooms may not be conspecific or the illustrations are wrong.  A unifying character is that Macrolepiota mastoidea also has a pronounced knob in the centre, resembling a female nipple (mastoidea means ‘breast-like’). However, as can be seen from the photographs above, that character is not always well pronounced. I think the illustration in Chandrasrikul et al. (2008, Mushrooms and Macrofungi in Thailand) shows the same taxon as the one at Dokmai Garden, and I believe they are right in naming it Macrolepiota gracilenta. Only a DNA analysis will resolve the question whether M. gracilenta and M. mastoidea are conspecific or not. Another possibility is that the Thai mushroom is a new undescribed species. I have collected a handsome specimen (the one in the top picture to the far left) to be sent to Uppsala University for analysis.

Is it a treat? Since I concluded this is a parasol mushroom (a Macrolepiota) and not a vomit mushroom (Chlorophyllum molybdites) I fried a cap and served it on toast with butter, drinking a glass of beer with ice. A superb treat, and still no gastrointestinal symptoms after three and a half hours of consumption. Although this is not a beginner’s mushroom due to the confusing characters, I conclude it is a choice mushroom and I propose the English name ‘gracile parasol’.

The characters are: a forest dwelling mushroom seen at the end of the rainy season, with a strikingly slender stipe (1 cm broad) which is seemingly white but with minute brown scales, a cap with minute grain-like scales, white gills and white spores.

Text & Photo: Eric Danell

2 Comments leave one →
  1. August 26, 2015 6:39 PM

    What about Macrolepiota dolichaula, it occurs in Thailand, India, China, Australia, its common in grasslands and can be large.

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