Panaeolus (Copelandia) tropicalis has been a thorn in my side for ages.  The published descriptions are vague, conflicting in some details and in French and German.  After examining dozens of collections, I was beginning to suspect that P. tropicalis wasn't even a real species and just a variety of P. cambodginiensis. 

BUT!!! now that I have actually seen one, its completely obvious when viewed under the microscope.  I instantly knew something was different when I first placed the specimen under the microscope, even at 100x magnification.  The metuloids (pleurocystidia) are nearly solid black (actually a very dark reddish brown).

I'll be putting together a microscopy guide for the 4 species of Copelandia (cyanescens, cambodginiensis, bisporus and tropicalis) for future reference.

Notes below:

Andaman Islands, India




This specimen has exceptionally thick walled Pleurocystidia, which is characteristic of Panaeolus tropicalis.  This is the first convincing specimen I have observed so far.  The specimen is badly contaminated and decayed.  No cheilocystidia were observed but are assumed to be present.  Isolation attempts to procured a more pristine specimen are underway.

From Gerhardt: (translated from German)

Quote:

Panaeolus tropicalis is mainly characterized through the typical form of the Metuloids. Their thick-walled shape and the conical top which is later completely filled with wall material are unique within the subgenus.

---

Drawing of P. tropicalis metuloid from Gerhardt


For comparison, the image below is what could be considered a typical Copelandian metuloid.  This example is P. bisporus but P. cyanescens looks nearly identical.




Previously I had misidentified a specimen of Panaeolus cambodginiensis as P. tropicalis in this thread.

http://www.shroomery.org/forums/showflat.php/Number/6950069#6950069