just checked the Botanicus website of the Missouri Botanical Garden, which I do periodically, and they are putting online early volumes of the American Fern Journal. Volume 1 (1910) to volume 11 (1921) are now available to read online or download as pdfs.
If you do not already know the Botanicus site, it provides a wealth of out of copyright botanical literature, including, of course, much of fern interest. The material is provided as (usually) very high quality scans, so that detail of figures etc is beautifully clear. You can search the material for species, keywords etc, although I do not find this search facility entirely reliable.
The site is rather addictive!http://www.botanicus.org/browse