According to Species Fungorum, Mycena alcalina (Fr.) P. Kumm. is not a current name. It is a valid synonym for the current Phloeomana speirea and has invalidly been used to mean Mycena silvae-nigrae, M. stipata, and M. maculata. I think it is best to avoid the name M. alcalina. P. speirea is a very small mushroom up to about 1 cm. M. maculata is also different and I think your photos are of M. silvae-nigrae or M. stipata, which both smell alkaline.