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The taxonomy and nomenclature of the genus Hydnophytum have not been revised since the early 1900s so there has been plenty of time for naming errors to creep in and get propagated along with the plants.  

One persistent mistake is misidentifying plants of Hydnophytum formicarum and Hydnophytum moseleyanum.  When I say H. moseleyanum I am referring to a complex of 6 or 7 closely related species that all look very similar to H. moseleyanum. These related species include: H. loranthifolium, papuanum, crassifolium, longistylum and philippinense. It is likely that most of these will get lumped together into H. moseleyanum in the revision of the genus that is currently being prepared in Europe.

Hydnophytum formicarum is a widespread species and shows considerable variation in some traits, including plant size and the nature of the caudex

The best way to tell Hydnophytum formicarum and moseleyanum plants apart is with leaf shape. leaf texture and leaf veins.


Hydnophytum formicarum leaves have a normal to leathery texture.  H. moseleyanum leaves are somewhat to quite succulent.


The three leaves on the left are from H. formicarums. The three leaves on the right are typical H. moseleyanum leaves. This photo is of the lower leaf surfaces. Notice the differences in leaf shapes and the veins. On older H. moseleyanum leaves, like these, the veins are almost impossible to see on the lower surface of the leaves.


This next photo is a close-up view (upper leaf surface) of Hydnophytum formicarum on the left and H. moseleyanum on the right to get a better comparison of the veins. Notice the important fact that H. formicarum leaves have 6 to 12 pairs of veins on each leaf while H. moseleyanum leaves have only 3 or 4 pairs of veins on each leaf.




Young plants are easier to tell apart because of the obvious ridges on the caudex on many (but not all) forms of H. formicarum.  Hydnophytum moseleyanum types never have ridges on young plants.

The two plants on the left are Hydnophytum formicarums and the two pots on the right are Hydnophytum moseleyanums.




Notice also that the caudex on young Hydnophytum formicarum plants tends to be quite flat whereas the caudex on Hydnophytum moseleyanum plants gets taller right from the start. 

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  • 2 years later...

Leaf vein numbers are not  a useful guide to identify members of the H. formicarum complex. For example, the sunken taxon H. mindorense Merr., has 5 lateral veins. Also, J& H note 3-12 lateral veins on their formicarum concept in the recent revision. Leaf shape also is a poor guide especially for some of the Philippine taxa which i suspect will become full species. More chromosome counts may be helpful.. 

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