This is quite a unique fern family with many charismatic species. There are three genera in Tennessee from this family. 

• Botrychium

• Botrypus

• Ophioglossum

Despite their differences in physical appearance, they share certain characteristics, such as, dimorphic fronds and gametophytes which get their nutrients from fungi instead of photosynthesis ("Guide"). 

The Grape Ferns. This genus has been under taxonomic scrutiny with many splitting the genus in two: Botrychium and Sceptridium. However, The World Flora Online states that the following species have the most up to date, accepted names. 

• Botrychium biternatum 

• Botrychium dissectum  

• Botrychium jenmanii  

• Botrychium matricariifolium

• Botrychium oneidense 

Regardless of which species you are dealing with, there are a few distinguishing features to help you differentiate it from the Botrypus and Ophioglossum genera. First, Botrychium has sterile leaves which exhibit some form of dissection, as opposed to the smooth margin of Ophioglossum ("Guide"). Second, the sterile frond of most ferns in the genus are evergreen, unlike the deciduous nature of Botrypus ("Guide"). Lastly, I think that the fertile frond of this genus is more "grape" like than that of the Botrypus genus- in that the sporangia are clustered in grape-like bunches. 

Rattle Snake Fern. This fern is very similar to members of the Botrychium genus, but there are ways to distinguish the two genera.  

One way to tell them apart is that Botrychium  is evergreen while Botrypus is deciduous  ("Guide"). A clever way to remember this is that rattle snakes don't come out in winter, so Botrypus won't be seen in the winter. Additionally, the sporangia 

• Botrypus virginianus 

Guide to the Vascular Plants of Tennessee. The University of Tennessee Press, 2015.