Arthonia molendoi s.l. growing on Xanthocarpia crenulatella s.l. from NE Mexico. This might be the first species of #lichenicolous #fungi that I identified. #Lichen "parasites" are challenging to deal with but the microscopic beauty of them its worth the headache

Captions clockwise. 1. Parasite and host on limestone. 2. Cross section before KOH. 3. Cross section after K, the host's epihymenium reacting purple and the parasite's tissues greenish. 4. Spores