176 REV. DAVID PAUL. 
microscope on the surface of the gills of any common Agaric 
like the field-mushroom. But if you wish to see them to 
the greatest advantage, you will select a Coprinus, such as 
C. plicatilis, which is often very common on lawns ; or, still 
better, C. radiatus, which is of frequent occurrence growing 
on decaying straw on a hotbed or dunghill. This last is so 
extremely tender and delicate that it can only be found in 
the early morning, for the sun shrivels it up in a very short 
time. In this little fungus, the structure of the hymenium 
can be studied to great advantage owing to the transparent 
thinness of all its parts, and, owing also to the fact that the 
spores stand out very conspicuously, being black. But the 
hymenium on which these basidia and spores rest is not 
always spread out on the surface of a gill as in the Agar- 
acini or Gilled-Fungi; you may have an arrangement of 
pores as in the Polyporei, embracing the genera Boletus, 
Polyporus, Deedalea, and so on, or an arrangement of spines 
as in Hydnum and others. In the Clavarie, of which the 
common Cl. rugosa or Cl. inwqualis may be taken as a type, 
the hymenium covers the whole surface of the clubs. But 
however varied the character and position of the hymenium 
may be, all the Hymenomycetes agree in possessing those 
basidia, each with its four sterigmata and four spores freely 
exposed. Among the Gasteromycetes, on the other hand, the 
basidia are inclosed in the structure of the fungus, and the 
spores when mature form the internal dust of the puff-balls. 
In the Ascomycetes again the spores, generally eight in 
number, are contained in the leng cylindrical asci which are 
familiar to every one who has viewed a thin section of a 
Peziza through a microscope. I need not go farther into 
detail; it is enough to give a general view of the system of 
classification, according to which the different groups of 
fungi are arranged. 
Let us return then to the Hymenomycetes, and select out 
of these the order Agaracini and the great genus Agaricus, 
and this for the purpose of making some observations on 
species which may be useful to the field botanist. Every- 
one who has paid any attention to the subject knows the 
difficulty there often is in identifying species of Agarics, 
to say nothing of the greater difficulties that attach to the 
