The Saprophytic Fungi of Eastern Iowa. 33 



from larger cells which associated together form a more or 

 less distinct fruiting surface or layer known as the hymenmni. 

 The order falls naturally into two sub-orders according as the 

 hymenium is or is not at the time of spore formation, or sepa- 

 ration enclosed by surrounding tissues. Hence we have — 



Hymenium exposed, IIymexomycetes. 



Type, the common Toadstool. 



Hymenium enclosed' in cavities of various sorts and sizes, Gasteromycetes. 



Type, the Puff-ball. 



The sub-order Hynioiomycctcs, according to the manner in 



which the hymenial layer is exposed, includes several families, 



thus: 



FAMILIES OF THE HYMENOMYCETES. 



Hymenium exposed on the surface of usually radiating plates 



or gills, lamellae, - - ■ - - - - - Agaricine^. 



Hymenium exposed on the inner surface of pits or tubules 



more or less deep, Polypore^. 



Hymenium exposed on the surface of papillre or teeth, - Hydne^. 



Hymenium spread over a branching, erect fructification, Clavarie^. 



Hymenium smooth, usually inferior and horizontal, - Thelephore.iE. 



Hymenium superior, lobed, convolute, or disk-like, gelati- 

 nous, (fertile threads not compacted into a true hyme- 

 nium) — Cooke, Tremelline^. 



x\s including more familiar forms we begin with the family 

 first named — 



The Agaricine^. 



I'he members of this family may for description all be com- 

 pared with the common Enghsh mushroom, and the terms 

 used in description are best defined with a plant in hand. 

 (Almost any of our larger native species will answer just as 

 well). We have in the first place the expanded umbrella- 

 shaped top — the pileus, mounted upon a stalk — the stipe. 

 The stipe may be centrally attached, as in the case now sup- 

 posed, or lateral, or wanting entirely, in which instance the 

 pileus will be fastened to its support {sub-stratimi) by margin 

 or top. Extending from the edge of the pileus to the stipe in 

 young unexpanded specimens will be found a web more or 

 less dense, at first, in typical specimens, completely concealing 

 the lamellae on the lower surface of the pileus. This web is 



