In June 2015, a lone fern appeared in one of my pots (see pictures below). It had 2 non-fertile leaves (known as trophophyll or trophophore). The long erected fertile stalk was an extension of the stalk from the non-fertile leaf. At the end region of the fertile was a spike where paired sporangia (spore-containing bodies) lined its length. Its leaves were more elongated than those seen previously.
In the 2009 Singapore flora checklist, there were 3 species of Tongue Fern listed, namely Ophioglossum nudicaule, Ophioglossum pendulum and Ophioglossum reticulatum. Ophioglossum pendulum usually grows on trees and is much larger in size than the other 2 Tongue Fern. According to the Flora of North America website, Ophioglossum nudicaule has 5-12 pairs of sporangia. As for Ophioglossum reticulatum, the number of sporangia was indicated to be 20-45 pairs by the Flora of Zimbabwe website. Based on the sporangia count and having only 2 choices left, this fern is identified as Ophioglossum reticulatum.
More than a year later in July 2016, the fern was still around in the same spot though several fertile spikes had come and gone.
 Sinha BMB, Srivastava DP, Jha J. Occurrence of various cytotypes of Ophioglossum reticulatum L. in a population from N. E. India. Caryologia 2009;32(2):135-146. | Read article |