2 NATURAL HISTORY BULLETIN. 



of some external injury to insinuate themselves into even the 

 living tissues of standing trees to their ultimate destruction.^ 



Species of the Polyporeaj are generally easy of recognition^ 

 characterized as most of them are by their more or less dis- 

 tinctlv tubular hvmenium. The various forms may also with 

 little difficulty be distinguished from each other usually by 

 characters largely superficial. Nevertheless, when any large 

 series is taken into account, the resemblance of contiguous 

 species and even genera is often puzzling enough. The 

 variations shown in well developed species are often consider- 

 able, especially among the Polypores proper. 



For the family the character already mentioned is reckoned 

 definitive, but in several genera the tubules are of such rudi- 

 mentarv development that a definition somewhat more ample 

 seems necessarv. Following the homology of the Agarics we 

 mav use the term pilcus to designate all that expanded part of 

 the sporocarp or fructification which is distinct from the hv- 

 menium. With this understanding we may define the family — 



POLYPOREiE. 



Pileus polvmorphic sometimes entirely wanting: the hvmen- 

 ium superficial, inferior, exposed as a lining on the inside of 

 open-mouthed tubules, pores or excavations variously devel- 

 oped, various also in shape, round or angular, isodiametric or 

 elongate: the basidia four-spored. the spores, as in the Agarics, 

 varying in form and color. 



The family Polvporea; includes several genera. Those 

 here to be discussed may be distinguished as follows: 



A. Tubules not forming' a stratum distinct from the bodv of the frtictijication. 



I. Sporocarp effused, membranaceous, pores mere 



pits formed by reticulating folds, . . . Merllils. 

 n. Pileus expanded, membranaceous; tubules at 



first papilliform, becoming elongate, . . Porothelium. 

 III. Fructification consisting of tubules onlv, the 

 receptacle entirely wanting; the tubules gre- 

 garious on the sub-stratum, and at first closed, Solexia. 



^See the works of Hartig, Sorauer, Frank, et al., especially R. Hartig, 

 Lehrbuch dcr Baumkrankheiten . 



