Lactarius volemus – Tawny Milkcap

The genus Lactarius is a widely and mnemonically known as ‘milkcap mushrooms’ for their unique characteristic latex emanation.

Common Name: Tawny milkcap, Voluminous-latex milky, Weeping milkcap, Apricot milkcap, Fishy milkcap, Bradley – The color of the cap ranges from orange-brown to yellow with age. The mushrooms that exude a milky colloidal suspension called latex are commonly called milkcaps.

Scientific Name: Lactarius volemus – The generic name Lactarius is Latin for milky, a reference to the latex secretion. The species name volemus is Latin for either “filling the hand” or “a kind of pear,” depending on the reference; it may be that it is both – a particularly large pear that fills the hand. While clearly speculative, this may be intended to convey that the amount of latex is enough to fill the hand, as this mushroom produces copious amounts. Another possibility is that the volemus pira (Latin for pear) was colored orange-brown or ‘tawny.’ The common name ‘voluminous-latex milky’ is in essence taking the Latin volemus as meaning voluminous, which is derived from volume and referred originally only to books; current usage allows for the notion of it meaning ‘in great volume.’ The scientific name is in the process of changing to Lactifluus volemus due to DNA assessments of the genus.

Potpourri:  The genus Lactarius is a widely and mnemonically known as ‘milkcap mushrooms’ for their unique characteristic latex emanation. A large grouping of at least 500 known species with some estimates of almost twice that many; it is a member of the Russula Family. Of all the milkcaps, L. volemus is probably of greatest renown, as it is very common in the northern temperate and boreal regions of Eurasia and North America, in the subtropical areas of Central America and Africa and the dipterocarp tropical forests of Southeast Asia. In France it is known as vache which means cow, likely due to its copious production of milk-like latex, as in ‘like milking a cow’. In Germany, it is known as brätling which translates roughly as ‘little roast’ which is probably a reference to color; this is sometimes extended to milch-brätling to emphasize the production of milk (milch). The American common name Bradley is most likely an Anglicized form of the German epithet. The Japanese name is chichitake which means ‘milk mushroom.’ It is also arguably the most recognized and collected Lactarius mushroom in eastern North America; it is easy to identify and it is edible.

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The voluminous milky is just that. When the gills are cut, white latex oozes out to form copious large droplets that fall to the ground like milky tears.

The Tawny Milkcap has a number of characteristics that facilitate a reliable identification, even though it can be somewhat variable in color and shape according to age and other environmental factors (which is true of most mushrooms). The orange brown cap which is technically called the pileus becomes depressed with age (physically not mentally) so that it has a vase-like shape that is very characteristic of many Russula Family mushrooms; the stem which is technically called the stipe is about the same color. The gills on the underside of the pileus are known as close in that there is very little spacing between; they extend down the stipe in a manner known as decurrent. When the mushroom gets older, it develops a fishy aroma. All of the above characteristics are helpful, but not all that distinguishing; what sets this mushroom apart is the latex. The voluminous milky is just that. When the gills are cut, white latex oozes out to form copious large droplets that fall to the ground like milky tears. The latex is also noteworthy in that it gradually turns brown, staining anything with which it comes in contact.

There are two other Lactarius mushrooms that resemble L. volemus and also produce significant amounts of white latex: L. corrugis, the Corrugated milky is named for its recognizable corrugated or wrinkled cap; and L. hygrophorus which has gills that are more widely spaced. Recent phylogenic research has revealed that L. volemus is actually a complex of many species that are closely related, so the presence of look-alike cousins should come as no surprise. As both are as edible as the Tawny milkcap and are typically listed as choice, this poses no problem for the committed (physically and not mentally although some would suggest the latter) mycophagist. It may seem counterintuitive that a mushroom that is filled with sap-like latex and smells like fish (which, even if you like fish, is generally considered unpleasant) would be a choice edible. The fish smell is volatile and therefore evaporates when the mushroom is heated above its boiling point by the cooking process. There are caveats, however. The most common method of preparing wild mushrooms is to sauté them in oil, a process that in this case results in the release of voluminous (literally in this case) quantities of latex into the pan. It is generally recommended that a slow cook boil be employed to retain the latex within the body of the mushroom, thereby enhancing the taste. Another problem is granularity. While most mushrooms have an elongated, fibrous cell structure that will bend but not break, mushrooms in the Russula Family have globular cells called sphaerocytes that are intermingled with the elongate cells. This imparts to them a granular texture in contrast to other mushrooms which have a texture that is similar to the pliability of meaty animal tissue. Charles McIlvaine, author of One Thousand American Fungi and a well noted mycophagist, provides that “the rich juices of Lactarii are best retained by baking; the species grow hard and granular if cooked rapidly. This method is preferable to stewing, but no one will despise a properly made stew of them.” Like most mushrooms, the gathering and preparing is worth the effort in terms of nutrition. 100 grams of Lactarius volemus contains about 25 grams of protein and only 4 grams of fat, with significant percentages of the USDA daily recommended amounts of iron, zinc, and manganese.

Why is it that some Russula Family mushrooms produce latex, specifically those in the Lactarius genus, whereas others do not? Latex is a chemically complex colloidal suspension that requires a fairly high investment in energy, something fungi must extract from their environment as they are not autotrophic like plants. Latex is a complex mixture of individual particles or colloids including but not limited to resins, fats, and waxes that are suspended in a liquid medium that contains dissolved hydrocarbons, proteins, sugars and alkaloids, among other things. Commercially, latex paints utilize this principle to convey coatings to a surface on the evaporation of the water carrier. About ten percent of all plants produce latex which corresponds to about 20,000 species in 40 families. Among the more noteworthy latex producing plants are the rubber tree (Helvea brasiliensis) from which natural rubber is derived, the gutta-percha tree (Palaquium gutta) from which the electrical insulator gutta-percha is extracted, the chicle tree (Manilkara spp) from which the latex was once used as the basis for chewing gum and the milkweed (Asclepias syriaca) which is eaten by monarch butterfly larvae but which is toxic to most other herbivores. It is the consensus among botanists that plants produce latex to forfend insect predators; a preponderance of the empirical observations supports this thesis. For example, the percentage of plants that produce latex in the tropics, where arthropods are ubiquitous is more than twice the percentage in temperate climates. Latex is released when plants are injured, a fact that is used by harvesters in tapping trees to extract latex. Similarly, a feeding insect will seek to penetrate the plants outer cells, automatically triggering the defensive flow. The latex is generally sticky to the detriment of insect mandible articulation and coagulates into a solid gel to cover the incision and protect the underlying tissues. But most important of all is that latexes are typically comprised of toxic chemicals that vary from plant to plant. It should really come as no surprise that plants produce latex to protect themselves; they produce thorns for the same reason.

The question is, can the latex insect defense thesis extend to the fungi of Kingdom Eumycota? This will at present remain a hypothesis, as there has been very limited research conducted on the mushrooms in the genus Lactarius, even less on their exudate latex. The voluminous quantity of latex from L. volemus has elicited some interest from the rubber industry, as the polyisoprene can be used as a low molecular weight model for the more complex commercial rubbers according to a 1998 Tokyo University paper. As a matter of interest, you could technically make a form of rubber from at least some of the milkcaps, but the quality would be in question and the quantity insufficient for commercial application. Another way to approach the latex etiology question is through exclusion: if latex is not created to ward off predators, then what is it for? In the Darwinian struggle for life, mutations occur when they promote propagation. If the latex does not protect against predators, then it must then improve profligacy. In the case of mushrooms, this would mean an ameliorable dispersal of reproductive spores. This is not unheard of in the fungal community as a number of species employ deliquescence (biological melting) in this way. Most notably, the stinkhorns evolved stink to attract flies to their oozing mixture of spores and fluidized thallus to promote reproductive dissemination. However, milkcaps do not deliquesce and they release extensive latex only when punctured. Another telling observation is that milkcaps are evolved from mushrooms that produce no latex in the Russula family. One frequently encounters a red Russula with evidence of having been eaten; a milkcap rarely if ever. My theory is that latex detracts slugs, one of the key nemeses of mushrooms.

The advent of DNA testing has wrought havoc with the traditional Linnaean taxonomies based on morphology; this is especially true among the fungi, the Family Russulaceae is no exception. The family consists of ectomycorrhizal (they enclose plant roots externally for nutrition) basidiomycetes (Basidiomycota is one of two subphyla of fungi) that have a cell structure composed of sphaerocysts, which, as their name implies, are spherical. This cell structure is uniquely distinct from that of other mushrooms, which have a fibrous structure and are therefore tough. It is hypothesized that the formation of sphaerocytes occurred due to evolutionary pressures to more rapidly expand the epigeal (above ground) fruiting body to expedite spore dissemination. Russulas break rather than tear due to the discontinuities that the spheres afford; they are widely called brittlegills. The taxonomy of the Russulas was thought to be simple. If it had latex, it was in the genus Lactarius; if it lacked latex, it was in the genus Russula. As it turns out, this is incorrect. Recent molecular phylogenic studies have revealed that there are four distinct clades within the Russula family. A clade is a relatively new term that is used to indicate all of the species evolved from a single ancestor; the relationships are clarified in cladograms, which are what family trees had always intended to be. Not only is there now a proposed new genus Multifurca (characterized by multiple furcations or forks in the gills) which will contain former members of both Russula and Lactarius, but the former Lactarius is now two genera, with the majority of the species in the new genus named Lactifluus. While changing to the new genus would have been technically correct, a 2013 Scripta Botanica article “Not every milkcap is a Lactarius” captured the emerging zeitgeist of taxonomic overload: “… in an era where we discover that widely accepted and long-known fungal genera and families are artificial, the idea of changing the concept of the two large agaricoid genera in this russuloid clade, is a larger shock to many mycologists than other changes to the Russulales have been.” The official decision was fortuitously made by the International Committee of Nomenclature to retain the original genus name Lactarius which would continue to include the majority (about 80 percent) of the milkcaps, while the minority would be banished to Lactifluus. To prevent confusion, the new Lactarius genus is to be called Lactarius sensu nova, which is probably necessary for clarity but adds to the tangled web of taxonomic distinctiveness. One of the unfortunate consequences of this change is that L. Volemus is in the smaller genus, and will henceforth be known as Lactifluus volemus, which will have profound lexicographic impact among fungus aficionados.

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The Pepper Milkcap  is aptly if euphemistically named for a pungent spice; the latex is one of the most acrid substances that one is likely to encounter outside a chemical plant.

As a further complication, the type species of the original genus Lactarius was L. piperatus, or peppery milk cap, almost as well-known as the tawny milkcap but for a different reason. It is aptly if euphemistically named for a pungent spice; the latex is one of the most acrid substances that one is likely to encounter outside a chemical plant. Where it stands on the Scoville scale has not been determined, but one touch to the tongue or lips will be enough to deter any further experimentation. It is quite common. In One Thousand American Fungi, Charles McIlvaine avers that he was first attracted to toadstools (a term that he uses for mushrooms in keeping with general Anglo Saxon mycophobia) by the appearance of so many pepper milkcaps after a forest fire in West Virginia in 1881 that they the “blackened district was made white.” And, in what may be one of the first occurrences of fungal use for fertilization, he “collected it then in quantity and used it, with good results, as a fertilizer to impoverished ground.” Surprisingly, pepper milkcaps are considered “edible with caution,” the caution being to parboil them extensively to volatize the latex. McIlvaine notes that they are eaten in most countries and that it is “good food when one is hungry and cannot get better. It is best used as an absorbent for gravies.” Not an altogether glowing endorsement. David Aurora in Mushrooms Demystified is characteristic of most other admonitions: “it is difficult to digest and may even be poisonous if not properly prepared.” You only go around once in life – however, the circuit can be significantly shortened by rashness