The University and Jepson Herbaria
The Rothfels lab is affiliated with the University and Jepson Herbaria at UC Berkeley, where Carl is a curator. The herbaria house approximately 2.2 million specimens including a very strong (and inordinately well curated) fern and lycophyte collection. Available from the UCJEPS website are links to myriad databases, the Jepson Workshops and the Botany Lunch Seminar schedule.
UCJEPS also hosts the Consortium of California Herbaria (CCH) site, which provides access to over 2 million digital specimen records of California plants, and to the Jepson eflora, the foremost authority on the vascular plants of California. Through the eFlora, one can access taxonomic treatments, distribution maps, illustrations, photographs, and online identification keys for Californian vascular plants, and the latter can be set to only include species from particular California bioregions.
Regional Herbaria Consortia
Aside from the CCH, other important somewhat-local sources for specimen-based plant diversity data include the Consortium of Pacific Northwest Herbaria and the SEINet network. For those working on broader scales, the Global Biodiversity Information Facility (GBIF) provides access to over 200 million biodiversity records, most of them georeferenced, complete with exporting and mapping tools.
Ferns of the World
For anyone interested in ferns or lycophytes (and, let’s face it, who isn’t), a must-visit resource is Ferns of the World, where one can find gorgeous photos of an surprising proportion of the World’s seedfree vascular plant diversity, as well as a wealth of associated information.
For those interested in technically-oriented fern photographs (and those of non-ferns, too), another site to explore is the venerable plantsystematics.org.
Encyclopedias of Life
There are a few resources devoted to presenting information on global biodiversity. I’m personally partial to the Tree of Life Web Project (tolWeb), and unsurprisingly, to its fern pages, like those of the notholaenids. A somewhat similar site is the less phylogenetically-oriented Encyclopedia of Life (EOL), and for those interested in contributing their own observations to those of a global network of citizen scientists, iNaturalist would be for you.
Nomenclatural and Official-Lists Resources
Natureserve Explorer provides information on the distribution, ecology, and rarity of North American plants (and animals, too, for that matter). Among its most useful features is a list of the global (G), national (N), and state/provincial/territorial (S) rarity ranks for all recognized taxa, from both Canada and the USA.
Index Herbariorum provides contact information and collection summaries for the world’s herbaria.
And a series of sites provide vital information on the nitty-gritty of plant nomenclature. These include Missouri Botanical Gardens’ TROPICOS, where one can find nomenclatural information (and synonym suggestions) for most plant names, the International Plant Names Index (IPNI), which serves as a repository for all validly published species- and genus-level names, Index Nominum Genericorum (ING), and for names of ranks above that of genera, the euphonious Indices Nominum Supragenericorum Plantarum Vascularium.