This post may contain plot details and quotes from The Signature of All Things.
The first five pages of Part 3 focus on mosses with an intensity that covers a wide breadth of topics.
We are regaled with the fact that mosses are "effortless to transport". They are not only small and light, but easily dried and thus avoid spoilage. Due to these qualities, mosses have been used as packing material for goods and other plants for centuries. The Whittaker botanical company also took advantage of these mossy features, using them to ship plants. Thus Alma not only traded and imported mosses herself, but she was able to mine the crates stored in her family's warehouses, which were filled with dried mosses from around the globe.
After years of study, Alma accumulated an extensive herbarium. She collected over 8,000 species of mosses, which seems to me a pretty high number considering Alma is written to have worked about 150 years ago. Currently the number of species of mosses is close to 12,500, so that puts Alma at having collected and identified 64% of present day moss species diversity. All without leaving her home in Pennsylvania. I wonder how many species of moss were described by 1848? I am not sure where I would even go to try to locate that fact? A species count from Hedwig would be too early, whereas Brotherus would be too late. Who would have been a contemporary bryologist of Alma Whittaker, living and working during the first half of the 1800's? I will have to do some digging around to see what bryological history I can uncover.
Alma also writes several books that as a bryologist I would most certainly have on my shelf. By 48 years of age she has written The Complete Mosses of Pennsylvania and The Complete Mosses of the Northeastern United States and has just begun work on The Complete Mosses of North America. The titles of the books could have been a little more creative or perhaps variable, but the sense of her productivity is firmly established.
In leu of these imaginary books, I would recommend these real identification guides for exploring mosses in Pennsylvania and the Northeast: Outstanding Mosses and Liverworts of Pennsylvania and Nearby States and Common Mosses of the Northeast and Appalachians. As for a good field guide that tackles mosses across all of North America, there are not any that I particularly like. Also a book covering mosses across the entire continent would be a pretty large tome to tote around in the field. My personal preference for identification is a regional guide with a more limited set of species to sift through. If you have a smartphone and internet access, a light field option with wide coverage could be the online Bryophyte Flora of North America. A key to the genera is posted here. Unfortunately all the links are broken and thus it is not connected to the descriptions. The full descriptions are arranged by family here, but you need to know the connections between the two to make them work together. The key is preliminary, so hopefully they will be linked in the final version.