#067: Mushroom Morpholgy: Verpas

The genus Verpa contains just a handful of species that are encountered occasionally.  These mushrooms look a lot like morels (FFF#033), but are attached just at the top of the cap and have a stipe filled with cottony material.  The cap of a verpa hangs down around the stipe, rather like a thimble on top of a finger.  This arrangement has led to the common names “Thimble Cap” or “Thimble Fungus,” although I usually just call them “verpas.”  Verpas tend to appear just before morels, so if you find one you should come back to check for morels after a week or two.^1–3

Description

All species of Verpa are small to medium-sized mushrooms (up to 15 cm tall) with a cap that hangs down around the stipe and a stipe that is filled with cottony material.  The cap is attached only at the top and is conic to bell-shaped.^1,2  The center of the stipe becomes more cottony as the mushroom ages, so young and fresh specimens sometimes appear solid.  Even when the stipe appears solid, the center is much less substantial – cut it in half and your knife will squish the central material into clumps.  Very old specimens may be completely hollow.³  Just checking the cap attachment and stipe center is enough to distinguish the verpas from all potential lookalikes.^1,2

There are several species of Verpa, but only two are common in North America: Verpa bohemica and V. conica.^1,2,4

V. bohemica has a highly wrinkled cap that is yellowish to brown.  Sometimes the tips of the ridges are a darker shade of brown.  The stipe is creamy white to yellowsh and usually darkens with age.  V. bohemica is very interesting under the microscope because it features enormous spores (up to 85 µm!) and has two-spored asci (most asci make eight spores).^2,5  The spores are so big you can actually see their shape using just a hand lens!  This species is commonly known as the “Wrinkled Thimble Cap.”  Some people call this species the “Early Morel,” but I prefer saving “morel” for true morels in the genus Morchella.²

V. conica has a cap that is smooth to slightly wrinkled and tan to dark brown.  The cap is not nearly as wrinkly as that of V. bohemica, so there is no chance of confusing the two species.  The stipe is creamy white to yellowish and typically becomes darker as the mushroom ages.^2,3,6

There are other species of Verpa, but only two have records from North America on Mushroom Observer: V. chicoensis and V. digitaliformis.^4,7,8  V. chicoensis is similar to V. bohemica but its wrinkly cap develops smoky colors with age.  Both Mushroom Observer records are from California.^7,9  V. digitaliformis is similar to V. conica but features a cap dotted with tiny pits (at least, that’s how the name is used on Mushroom Observer – Persoon’s original description says the cap is wrinkled but not honeycomb-like; the usage may have changed since 1822).  This species is recorded from both North America and Europe on Mushroom Observer.^8,10,11

Ecology

Like morels, the ecological role of Verpa has not been fully figured out.  Mycologists assume that verpas are mycorrhizal, since they grow from the ground in forests (both hardwood and conifer).  Verpas appear in early spring before morels, or during winter in warm climates like the West Coast of North America.^2,5,6  None of the species are common, but they can be found all across the northern hemisphere.^2,12  It took me five years of mushroom hunting before I finally saw a verpa, which gives you an idea of how uncommon these mushrooms are.  When I did finally find V. bohemica the patch I found produced about 100 mushrooms over the course of a week, so you can still find a lot of these mushrooms even if you don’t see them very often.

Similar Species

V. bohemica bears a striking resemblance to morels, especially Morchella punctipes (the Half-Free Morel, FFF#211).  Two factors easily separate verpas from morels: 1) verpas have a cap attached only at the tip while morels have a cap attached all the way to the base and 2) the stipe of a verpa is filled with cottony material while morels are hollow with a single cavity that runs from the base of the stalk to the tip of the cap.  Additionally, V. bohemica has a wrinkled cap rather than a cap with distinct ridges and pits found in the morels.^1,2,5

V. conica is a little more distinctive thanks to its smooth cap.  You might confuse it with Leotia lubrica (FFF#188), although that species appears later in the year, has a slimy or gelatinous texture, and a cap that is more lollipop-like than thimble-like.

Verpas are also somewhat similar to false morels (FFF#034) and elfin saddles (FFF#035), which also have caps that attach only to the top of the stipe.  False morels and elfin saddles can be easily distinguished by their caps that are highly lobed and stipes that are solid or chambered.

Edibility

There are mixed opinions on this group’s edibility.  Some authors report verpas to be edible (only after being cooked), while others report them to be poisonous.^2,3,13  People tell me that eating verpas is becoming more common with hardly anyone having a bad reaction, but I have no real evidence to support that claim.  Symptoms of verpa poisoning are variable and may include gastrointestinal upset and loss of coordination.²  However, this may happen only when people eat too much of the mushrooms.¹³  If you choose to eat verpas, remember to try just a little bit the first time to determine how your body reacts to the species.

I have tried eating V. bohemica a couple times.  I did not have any reactions, but I ate them in small amounts.  The texture of the mushrooms was good, but the taste was not distinctive.  If you choose not to eat this mushroom, you’re not missing much.

Taxonomy and Evolution

Verpa is placed in the family Morchellaceae, which also includes the morels (Morchella spp.) and the cup fungus genus Disciotis (see FFF#139, Disciotis venosa).^1,4  Given how closely verpas are related to morels, it is perhaps no surprise that they look so similar.  Verpas actually give us a hint about how morels evolved from cup fungi.  First, the cup evolved a stalk to hold it above the ground, giving it better access to air currents.  Next, the cup evolved to hang down around the stipe (like V. conica).  Then the cup developed wrinkles to increase the surface area (like V. bohemica).  Finally, the cap fused with the stipe to complete the morel shape (which probably uses less material and saves energy).¹⁴

Kingdom	Fungi
Subkingdom	Dikarya
Division (Phylum)	Ascomycota
Subdivision (Subphylum)	Pezizomycotina
Class	Pezizomycetes
Subclass	Pezizomycetidae
Order	Pezizales
Family	Morchellaceae
Genus	Verpa Sw.4
Species	Verpa bohemica (Krombh.) J. Schröt.15 Verpa chicoensis Copel.16 Verpa conica (O.F. Müll.) Sw.17 Verpa digitaliformis Pers.18