“Microgramma C.Presl is a fern genus of approximately 30 species in the family Polypodiaceae, all occurring in the Neotropics except one occurring in Africa. They are rhizome-creeping epiphytes, growing from trunk bases to the canopy, with a few species also able to grow in rocky or terrestrial habitats. They occur preferentially in wet tropical forests but also colonize dry forests and savanna environments across a broad area of South America and tropical Africa […]”. (Almeida e.a. 2021)
Microgramma nana, the dwarf Microgramma, does particulary well in hermetospheres. It was first described in 1849 as Acrostichum nanum (Liebmann 1849), later regarded as a variant of Microgramma tecta, and recognized in 2018 as a distinct species based mainly on differences in the indument (Smith e.a. 2018), the shape and position of its scales (see picture below). Based on molecular phylogeny, its closest relatives are M. tecta, M. tobagensis and M. piloselloides (Almeida e.a. 2021).
![".[...] subulate blade scales, these usually geniculate, rarely applanate [...]" (Almeida e.a. 2021) as one distinguishing feature of Microgramma nana vs. M. tecta; 5-litre jar dedicated to Costa Rica, 07.03.2024, 559 days after onset; stacked from 6 images.](https://hermetospheres.com/wp-content/uploads/2024/03/m_nana_240307_scales_br22s4.jpg)
Scientists are still largely in the dark as to what function these scales and hairs (trichomes), which are found on both the fronds and the rhizome of M. nana, fulfil. Numerous hypotheses have been brought up (e.g. protection against high levels of solar radiation and thereby against desiccation, absorption of water; Carvajal-Hernández 2018). However, there is hardly any experimental data to support these hypotheses.
It is always surprising how little contact with the substrate ferns like this one need in order to thrive.
And for once, the dirty glass panes are welcome in the picture, because they give the hermetosphere an impression of cloud forest:
Hermetospheres 
One response to “The dwarf Microgramma”
[…] experiences with Microgramma ferns in closed terrariums are mixed: While M. nana thrives for years in a container, M. vacciniifolia grew some hairy rhizomes but never proper […]
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