Resources for Hornworts

There are about 5 species of hornworts in British Columbia, with their numbers increasing as you head sound. Hornworts are ephemeral things that seem to only be prominent (or as prominent as a 1cm plant can be) in the spring when their large horns/sporophytes are developing.

Where and when to look for Hornworts
In coastal British Columbia, hornworts seem to show up in February and March and loiter until early summer around seeps over thin, finer soil and rock. There are also records all over the west for agricultural fields-- presumably soils of the moisture retentive "clod" type.

What you need to identify Hornworts
Ideally you will have fertile material with mature spores. You will know you are at the right stage when the long sporophyte begins to dehisce and reveal the spore mass within. Barring that, you can look for little bulbils (asexual propagules) on the underside of the thallus. The shape of the thallus and the abundance and form of the protuberances can also be helpful. The three genera of this region can be distinguished based on the presence of the bulbils (Phymatoceros bulbiculosus) and, in the species lacking those bulbils, the colour of the spore mass: yellow in Phaeoceros and black in Anthoceros.

Hornwort ID resources

• @david1945wagner 's Hornworts of Oregon guide includes visual key to all species that are likely to be found between BC and Oregon. There is particular emphasis on spore ornamentation, which is crucial for ID to species in some cases. The site is also rich with complete and visual species descriptions, contemplations and relevant literature. This is my first stop.
• Doyle and Stotler's 2006 Treatment of the Liverworts and Hornworts of California
• Hornwort taxonomy seems particularly plagued by ephemeral names and synonymy. This Stotler and Crandall-Stotler 2005 paper is a good place to try and relate one name to another. It also gives a summary of all species recorded in North America as well as their distributions
• General hornwort biology, morphology, anatomy and classification is well covered and abundantly referenced in this 2020 review paper by Frangedakis et al. (open access).

Hornwort Databases

Like mosses and liverworts, hornwort collection records and distribution maps can be excavated from the Bryophyte Portal.
• Likewise, a search through the Hornwort section of the Bryophytes of the Pacific Northwest iNaturalist project erected by @johndreynolds will give you a sense of what to look for, where to look and when to look.

A final comment about collecting
There are only about 50 records of hornworts in herbarium collections for the province of British Columbia. Their diversity, distribution, ecology, phenology et al. are not well understood in our region, so any records for this group are worth collecting provided the population is vigorous and you have permission/permits to collect where applicable. Below you can see @jstraka 's recitation of a helpful rule: "The rule of thumb I have heard for collecting (at least for plants) is the "1 in 20" rule - The further comments below by @david1945wagner clarify the rule "It is a rule of thumb that you should find at least 20 individuals before collecting just 1. There should be 40 present to collect 2. It's a rule of thumb, meaning to be applied on a case by case basis. If applied strictly, it might result in populations of a rare species reduced to 19. With lichens or bryophyte colonies it may mean to take only 5% of the patch or thallus." The full write up of the rule can be found down the page here in a 1991 issue of the Plant Science Bulletin from the Botanical Society of America.

You should collect and send hornworts that meet these criteria to your regional herbarium. If you have questions about this, feel free to contact me. Instructions for submitting material to the UBC Bryophyte Herbarium, for example, can be found here.

Posted on January 3, 2023 08:56 PM by rambryum