From List of National Natural Landmarks, these are the National Natural Landmarks in Arkansas. There are 5 in total, 4 are forests, 1 is a spring.
Arkansas National Natural Landmarks (clickable map)
| Name | Image | Date | Location | County | Ownership | Description | |
|---|---|---|---|---|---|---|---|
| 1 | Big Lake Natural Area | 
|
1974 | 35°54′48.61″N 90°7′3.4″W / 35.9135028°N 90.117611°W | Mississippi | Federal | Forest area within Big Lake National Wildlife Refuge. |
| 2 | Lake Winona Research Natural Area | 1976 | 34°42′36.66″N 94°25′27.81″W / 34.7101833°N 94.4243917°W | Saline | Federal | Pine forest near Lake Winona (Arkansas); part of Ouachita National Forest. | |
| 3 | Mammoth Spring | 
|
1972 | 36°29′52″N 91°32′09″W / 36.4978°N 91.5359°W | Fulton | State | The largest first magnitude spring in Arkansas, it is connected underground to the Grand Gulf State Park in Missouri. |
| 4 | Roaring Branch Research Natural Area | 1976 | 34°22′22.8″N 93°58′40.8″W / 34.373000°N 93.978000°W | Polk | Federal | Steep ravine with a virgin forest in Ouachita National Forest. | |
| 5 | White River Sugarberry Natural Area | 
|
1974 | 34°21′0″N 91°6′0″W / 34.35000°N 91.10000°W | Desha | Federal | Virgin hardwood bottomland forest in White River National Wildlife Refuge. |
Well, that’s interesting to know that Psilotum nudum are known as whisk ferns. Psilotum nudum is the commoner species of the two. While the P. flaccidum is a rare species and is found in the tropical islands. Both the species are usually epiphytic in habit and grow upon tree ferns. These species may also be terrestrial and grow in humus or in the crevices of the rocks.
View the detailed Guide of Psilotum nudum: Detailed Study Of Psilotum Nudum (Whisk Fern), Classification, Anatomy, Reproduction