Sometimes treated as a single genus (Gentiana), the gentians in the northeastern United States are taxonomically split by most authors into three genera: Gentiana, Gentianella, and Gentianopsis. Before I get to the fringed gentians, let's look at how the three genera, in the strict sense, differ.
The photograph above shows an open flower of Gentiana saponaria. The flowers of this species are usually more closed than this, but this photo nicely shows one of the important characteristics of the genus Gentiana when separating it from Gentianella and Gentianopsis. Between the corolla lobes, you will see membranaceous appendages. Gentiana, sensu stricto, has teeth, appendages, or plaits between the corolla lobes, while Gentianella and Gentianopsis lack this character. Also, members of the genus Gentiana are perennial, while those of the genera Gentianella and Gentianopsis are annual or biennial.
Gentianella amarella is shown in the photograph above. As stated previously, members of the genera Gentianella and Gentianopsis lack the appendages between the corolla lobes that are present in members of the genus Gentiana. To distinguish Gentianella from Gentianopsis, look at the corolla lobes. Gentianella does not have fringed corolla lobes, while the corolla lobes of Gentianopsis are fringed along the sides and often around the top.
You can see in the photograph directly above and those below that the corolla lobes are conspicuously fringed, so all of these photos show plants in the genus Gentianopsis. The photograph above shows Gentianopsis crinita, Fringed Gentian. The photograph quality is poor, but you can see that the corolla lobes are fringed across the top and along the sides with long (2-6 mm) linear segments. You can also see broad, lance-ovate leaves (often more than 1 cm wide)characteristic of this species.
Above is a close-up of the flower of Gentianopsis procera, Lesser Fringed Gentian. Notice the long, linear fringes on the sides of the corolla lobes, but the short (less than 2 mm), irregular, broad-based fringes along the top of the corolla lobes. In the photograph below, you can see the vegetative distinguishing character between the two species of Gentianopsis. In Gentianopsis procera, the upper leaves are linear or very narrowly lanceolate (often less than 1 cm wide).