Cryptocoryne cordata siamensis The form of C. cordata
occurring in Thailand. Karyotype: 2n=68, 2n=102
Jan Bastimeijer and Joseph Bogner weighed in on C. cordata and using karyotype (= number of chromosomes) evidence have made a significant and sensible - given what we know - reclassification; there are still forms that have not gone expensive DNA analysis yet and almost certainly more forms of this highly variable plant still to be found.
So, the new breakdown goes like this:
C. cordata cordata is the 2n=34 krayotype and found in Southern Thailand, Penninsular Mayalsia and one known location in Sumatra. Mostly acid-loving blackwater plants.
C. cordata siamensis is the form from Thailand with a chromosome compliment of 2n=68,85,102 and forms exist that live in acidic black water while other forms exist from limestone biotopes and do well in hard water.
C. cordata grabowski is the n=68 other form from Borneo, nearly all of which are from black water peat swamps.
This cultivar showed up in a commercial shipment in the 1970s and was finally located in nature in Thailand around 2010. It's been shown (Eggler 2019, Wongso 2019, pers comms) that reduced illumination is a prerequisite for the famous veination pattern to display. In higher light they look like any other Crypt. cordata siamensis plants. The flowers are not unusual in any way, just the leaves.
