Russula emetica
Description
The Sickener mushroom is very common in coniferous woodlands across Britain, Ireland, mainland Europe, northern Africa, and some parts of Asia and North America. There are many types of Sickener mushrooms, but they're challenging to identify because they have a lot of species, and most of them are not well-studied. Some are collected for eating in certain European countries, but it's tricky to be sure which type you have just by looking at it.
One specific kind, called the Geranium Scented Russula, is considered poisonous by some sources. The Sickeners or Emetic Russulas can make you sick, as the name suggests. There's even one called Russula subnigricans, found in China, Japan, and the US, which is said to be deadly.
Identifying these mushrooms just by sight is really hard, and sometimes impossible. You might need a microscope to be sure about the type of Russula you've found. Before you try eating any Russula, you have to be absolutely certain it's a Russula because some mushrooms can be dangerous to eat.
Common names: The Sickener, Emetic Russula, Vomiting Russula.
Mushroom Identification
Cap
Scarlet, fading in wet weather (the pigment in the cap cuticle is somewhat water-soluble); peeling almost to center; the flesh of Russula emetica is pink beneath the cuticle; cap surface smooth, convex, sometimes becoming slightly depressed when fully mature; margin knobbly with small, rounded bumps irregularly spaced) and slightly striate; 3 to 10cm across.
Gills
White, turning pale cream; adnexed or free; crowded.
Stem
White, sometimes yellowing slightly with age; cylindrical, the base slightly clavate; 4 to 9cm long, 0.7 to 2cm in diameter.
Spores
Ellipsoidal, 8-11 x 7.5-8.5µm, with conical warts to 1.2µm tall linked by narrow connectives to form a well-developed reticulum. The spore print is white or very pale cream.
Look-Alikes
There are many, many russulas and many red russulas. It is often difficult to tell one from another. You can identify mushrooms in the genus Russula by their blocky shape and their brittleness. They will break apart in your hand like a piece of chalk. The stalk even looks like a piece of chalk.
Another of the ‘red for danger’ brittlegills, this mushroom is very similar in appearance to the Beechwood Sickener, Russula nobilis.
Differentiating features are the greater brittleness of Russula nobilis is just as poisonous as Russula emetica and so both should be avoided when gathering mushrooms for food.
Several other red-capped brittlegills can only be separated from Russula emetica by thoroughly following one of the specialist keys, and in many cases, microscopic characters such as spore ornamentation have to be studied using an oil-immersion lens.
History
First described in 1774 by German mycologist Jacob Christian Schaeffer, who named it Agaricus emeticus (most gilled fungi were placed in the Agaricus genus in the early days of fungal taxonomy), this mushroom was later transferred to the genus Russula by Christian Hendrik Persoon in 1796.
Synonyms of Russula emetica include Agaricus emeticus Schaeff., Russula emetica var. emetica (Schaeff.) Pers., and Russula emetica var. gregaria Kauffman.
Russula emetica is the type species of the Russula genus.
Russula, the generic name, means red or reddish, and indeed many of the brittlegills have red caps (but many more are not, and several of those that are usually red can also occur in a range of other colors!). The specific epithet emetica surely needs no explanation.
Photo sources:
Photo 1 - Author: James Lindsey (CC BY-SA 2.5)
Photo 2 - Author: Bob (Bobzimmer) (CC BY-SA 3.0)
Photo 3 - Author: peupleloup (CC BY-SA 2.0)
Photo 4 - Author: James Lindsey (CC BY-SA 2.5)
