Short Notes on Nature Singapore
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Short Notes on Nature Singapore

30 July 2017 | Swamp Fern | Cyclosorus interruptus |

photo Cyclosorus interruptus is commonly known as Swamp Fern due to its affiliation with swamp or wet habitat. After removing one of them from my potted area in February 2015, I still had another plant left which was doing quite well. It was originally confined to a mid-size pot but over the last one year, I had allowed its rhizomes (horizontal stems) to move across to adjacent pots at both sides. The migrated rhizomes had anchored itself and sprout fronds (leaves) in those pots. I am thinking of cutting it off from the parent plant to have another 2 separate plants.

photo At times, I continued to ponder over the identity of this fern in my pot. All seemed well except for the missing indusium (an umbrella-like cover) on the sorus (spore-producing structure). So far, I had yet to see an indusium though I might have missed. According to the Flora of Zimbabwe website, the indusium is small and often shed early.

photo The other feature often described in online resources of this fern was the presence of orange-red glands on the veins on the lower surface of the fronds. I scarified 2 fronds yesterday, a fertile one and a non-fertile one, to try to locate the mentioned glands. I assumed they were very tiny since my visual inspection did not yield anything. After magnifying the pictures taken, I could see some orange spots but could not exactly tell whether they were those mysterious glands.

One feature I did see was the flat scales on the underside of the pinnae (leaflet). They were position close to the midribs and only found on pinna that were at the lower part of the frond. They are probably the remnants of the same scales found on the rhizomes. A good illustration of the glands and scales could be found in a 2012 publication from Australia.

I will have to continue to monitor the fern to hopefully locate the indusium.

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