NOTES ON THE GENUS MYCENA.* 
7 
IVY MASSEIi. 
Up to the present time I have only examined about half the 
number of British species, but already have come to the 
conclusion that the present system of classification does not 
satisfactorily define the species. The primary sections of the 
genus are each founded upon a single character which is only 
characteristic of the typical form of each, and, like all other 
attempts at classification founded on a single character, 
proves to be of doubtful value. I have found that microscopic 
are more stable than macroscopic characters. 
Cystidia. — Many species of Mycena possess cystidia, and. 
so far as I have observed, their presence or absence is constant, 
as is also their shape. In this genus the cystidia, when present . 
are arranged in two ways : (i) scattered over the surface of the 
gill mixed with the basidia ; (2) confined to the margin where 
they are often arranged in clusters. This last arrangement is 
what constitutes the characteristics of the old section Calodontes. 
where the edge of the gill is bristly and coloured under a lens, 
due to the presence of cystidia containing colouring matter. 
Basidia. — In the majority of species the basidia have four 
sterigmata, but a few possess only two, as in M. galericulata . 
The basidia vary considerably in size in the different species, 
but are not considered of any value as a specific character. 
The Trama, or median portion of the gill, is always con- 
stant in structure in the same species, and sometimes affords 
important characters. In some cases it is composed of long, 
narrow cells, running parallel, and closely packed together, 
leaving practically no air spaces, as in M. ritgosa. When the 
trama presents this structure the gill is tough and pliant. 
In other species the trama is composed of very large, 
inflated subglobose cells, with numerous air spaces, as in M. 
galopoda. This structure is characteristic of brittle gills, the 
brittleness being due to the pressure of the cells on the un- 
yielding air spaces. This character is best studied in the 
genus Russula. 
Laticiferous hyphae are present in the gills of some species, 
and contain the white or coloured liquid called milk, such as 
is present in the group Lactipes. 
Spores. — The epispore in most species of Mycena has the 
>ame refractive index as water, consequently is not seen ; but 
a large globule which is usually present is sharply defined, 
and so in some instances, when the globule has been mistaken 
for the spore, the latter has been described as globose. A weak 
solution of iodine stains the spore wall and shows the true 
spore-form . 
* Abstract of paper read at the Sandsend Mycological Meeting, 20th 
September, 191s. 
1914 Jan. 1. 
