for the first view the difference is in the dark colour flower.
The plant is more compact then the typical caudatum, has normally only 2, very seldom 3 flowers and a trapezoid staminode very differen to caudatum.
The last difference is the region where this species comes from, Middle-America, Guatemala.
It was in trade and culture many years as Phrag. warscewiczianum or caudatum var. warscewiczianum, then again described as Phrag. popowii.
To my humble opinion I can recognize as a diferent specie just for the staminode.
If it was described as Phrag. warscewiczianum or caudatum var. warscewiczianum, why it has a name as Phrag popowii. Is this accepted according to international nomenclature?
I personally think it should be named Phrag warscewiczianum, sorry not Phrag popowii wich is a very recent name and NON VALID....for many rasons.
Have a good day and thanks
There is another thread on this forum that deals with the whole warscewiczianum/popowii/wallisii debate.
But in short the plant shown here (that is native to Central America) was never officially described, so that is why we (Guido Braem, Sandy Ohlund and myself Robert Quene) described it and gave it the name Phrag. popowii. A different species (native to South America) with lighter colored flowers that was later known as Phrag wallisii, was originally described as Phrag. warscewiczianum (berfore it was described as Phrag. wallisii). Hence the name "warscewiczianum" should be used for that species.
Big confusion now
I clearly understand that Phrag wallisi is a valid specie, not to be named Phrag "other name", so still the name Phrag. warscewiczianum is "empty" and should be used for the plant you have described AND NOT ANY OTHER NAME...
This is just an personal opinion...
Have a good day