Earlier this week, my fern enthusiast friend, Fred from Germany, whom I befriended through my website, shared with me some pictures of a fern which he grew from spores collected from a commonly sighted fern at Clementi area. Fred had identified it as Cyclosorus papilio. At first, I thought that it might be Christella dentata since there was no report on Cyclosorus papilio in Singapore. However, some features of the lower pinnae (leaflets) did not match up with that from Christella dentata.

Both Cyclosorus and Christella are from the same family of fern known as Thelypteridaceae. In Singapore, there are a total of 17 ferns in this family listed in the 2009 Singapore flora checklist. Of the 17 in the list, there are 4 Christella species and one Cyclosorus species. However, the botanical names of some of these species had changed over time. It seemed that 14 of them have now come under the genus Cyclosorus. In the table below, I have omitted 3 species listed in the Singapore flora checklist but not not listed in the Ferns of Thailand website. The description of the rhizome is also obtained from this website.

To further investigate this common fern, I went to a nearby park yesterday to check out a fern (Cyclosorus subpubescens) that look rather similar to the one in Fred's pictures. I did not go to Clementi as it was rather far from my place. The main part of the fern to focus on was the pinnae near the base of the stipe. This fern is very common, at least in this park, especially on partially shaded wet land. It was so common that it even grew in my pots spontaneously over a period in the past. I had wrote a short note on it back in March 2014 on this fern. In fact, this fern was listed as common in at least 3 recent flora surveys in Singapore: (1) Punggol End Forest (2013), (2) Clementi Forest (2012) and (3) Lentor Forest (2013).

Indeed, the feature of the lower pinnae matched well. The Ferns of Thailand website described the lower pinnae of this fern as "small, butterfly-shaped". They do look like green butterflies.

The only feature that still puzzled me is the fiddlehead. I had seen some with thicker and longer hairs but some with finer hairs, which I suspect is due to the stages of growth. For now, I think the fern should be Cyclosorus subpubescens.

Just before I wanted to upload this note to my website, I came across a recently published (2014) article titled “The urban pteridophyte flora of Singapore” based on a survey done in 2010-2011. Christella subpubescens was mentioned in the article with synonyms indicated as Cyclosorus latipinna and Cyclosorus sumatranus. It did not mentioned Cyclosorus subpubescens as a synonym. All that was said about Christella subpubescens was the name and its synonyms. In the Plant List website, Christella subpubescens is an accepted name. However, Cyclosorus latipinnus is also an accepted name. Below is the table of names on Thelypteridaceae extracted from this article.

Amidst the confusion over the accepted botanical names of the ferns in the Thelypteridaceae family, I have named the ferns in my website based on that from the Ferns of Thailand website. Based on the information on the website, it is hosted by the Royal Botanic Garden Edinburgh with the content managed by Stuart Lindsay, Gardens by the Bay, Singapore and David Middleton, Singapore Botanic Gardens.

As for the 2014 article, it was consulted with the fern expert, Alan Smith from the University of California in Berkeley.

Update: 1 September 2024