"In the mid 90's, the Singapore Science Center published a picture of a Cryptocoryne on their website on threatened plants which was ascribed to C. griffithii. The first Cryptocoryne on the Red List in the Internet! But it didn't match very well the European idea on C. griffithii. In 1999 there was an opportunity to study the plant in its natural habitat with help of the National Board. The present idea on this plant is that it is an (natural) hybrid between C. nurii and C. cordata, both growing in Johore (Malaysia) but not in Singapore. "

"C. ×timahensis is only known from a pond of c. 10 by 3 m in the Bukit Timah Nature Reserve in Singapore."

"The locality in the Bukit Timah Nature Reserve is remarkable. C. ×timahensis grows near the top of the hill in a very tiny stream in an artificial pond which is formed by damming the stream. There are - up to now - no other localities known, so this plant is extremely vulnerable for any changes in the hydrological situation. Another aspect of C. ×timahensis is that the plant is never found fruiting. Pollen analysis turned out the the plant is fully sterile, so one has to deal with a hybrid (hence the cross in the name). Looking at the form, colour and structure of the limb of the spathe and the leaves, best candidates are C. cordata and C. nurii. These however are native in southern Johore (Malaysia). Even more remarkable is the chromosome count 2n = 54 for C. ×timahensis. You may have expected 2n = 51. based on the number 17, as normal for malayan species."

Literature https://crypts.home.xs4all.nl/Cryptocoryne/Gallery/tim/tim.html
Bastmeijer, J.D. and R. Kiew, 2001. A New Cryptocoryne Hybrid (Araceae) from the Bukit Timah Nature Reserve, Singapore. Garden's Bulletin Singapore 53(2001): 9-17.
Cheers, G. et al (eds), 1999. Botanica. Koenemann, Keulen (dutch edition). Tan, H.T.W., I.M. Turner, Y.C. Wee and K.S. Chua, 1994. Plants in the Singapore Red List. Singapore Scientist 72: 26-32.
Tan, H.T.W., 1995. A Guide to the Threatened Plants of Singapore. Singapore Science Centre, Singapore.