Species description:
Genus name in honour of John Bartram, a plant collector and gardener of colonial America. The species name describing the shape of the sporangium: like an apple.

Comments:
Commonly called "apple moss", because the unripe sporangium resembles a tiny apple.

Distinguishing characteristics:
The combination of the spherical sporangia and the long, slender, twisted leaves that diverge strongly when moist, combined with the bluish-green to yellowish-green colour, are usually enough to distinguish the species.

Habit:
Forming loose tufts and turfs; leaves much curled and twisted when dry and pale yellowish-green and wide-spreading when moist. Red rhizoids often abundant on the stems.

Similar Species:
B. ithyphylla has leaves with shining clasping leaf bases and the leaves are usually straight, even when dry. B. halleriana has the sporangia appearing lateral on relatively short seta, thus nearly buried among the leaves away from the stem apex. Although Philonotis has spherical sporangia, the leaves are short and triangular as is the case for Conostomum tetragonum. B. ithyphylla and Conostomum are confined to alpine and subalpine elevations. Plagiopus oederi is similar to Bartramia but plants tend to be dark green rather than pale green; the leaves ap­pear to be in three irregular rows and lack an expanded base, and the plants grow mainly on calcareous cliffs (Bartramia is usually on acidic rock.) Anacolia menziesii has sporangia that lack peristome teeth, the sporangium surface is not grooved, and the leaves are not twisted when dry; the plants are usually a rusty, yellowish-green and stems are heav­ily invested with red-brown rhizoids.