Close-up views:

The eBook titled "100 Common Vascular Plants of the Nee Soon Swamp Forest" published in 2013 by the then Raffles Museum of Biodiversity Research (RMBR) mentioned another species of Agrostistachys, namely Agrostistachys indica. As I could not tell the differences between the 2 of them at the moment, some of the pictures above may be Agrostistachys indica. Both species were listed in the Checklist of the Plant Species of Nee Soon Swamp Forest published in the same year.

In a book published by RMBR in 2012 (page 94) on Singapore's rainforest [3], the botanical name Agrostistachys sessilifolia was used. Interestingly, the Checklist of the Vascular Plant Species of the Bukit Timah Nature Reserve published in 2011 [4] and the biodiversity survey published in 2019 [5] only listed Agrostistachys borneensis.

All 3 names (Agrostistachys borneensis, Agrostistachys indica and Agrostistachys sessilifolia) are accepted names in the Plant List website which mean that they should be 3 distinct species. I will await someone to shed some light on whether there are really 2 species of Agrostistachys in Singapore and if so, the differences between the two of them.

References:

[1] Tan SY, Koh CY, Siow HJM, Li T, Wong HF, Heyzer A, Tan HTW. 100 Common Vascular Plants of the Nee Soon Swamp Forest, Singapore. 2013.

[2] Wong HF, Tan SY, Koh CY, Siow HJM, Li T, Heyzer A, Ang AHF, Ismail MR, Srivathsan A, Tan HTW. Checklist of the Plant Species of Nee Soon Swamp Forest, Singapore: Bryophytes to Angiosperms. 2013.

[3] Wang LK, Yeo DCJ, Lim KKP, Lum SKY. Private Lives: An Expose of Singapore's Rainforests. Raffles Museum of Biodiversity Research, Singapore. 2012.

[4] Turner IM, Chua KS. Checklist of the Vascular Plant Species of the Bukit Timah Nature Reserve. 2011.

[5] Ho BC, Lua HK, Ibrahim B, Yeo RSW, Athen P, Leong PKF, Ibrahim A, Koh SL, Ibrahim H, Lindsay S, Chin LL, Seah WW, Middleton DJ. The plant diversity in Bukit Timah Nature Reserve, Singapore. Gardens’ Bulletin Singapore 2019;71(Suppl. 1):41-134.