PORES WITH THIN WALLS. 



One series, which we call Ponderosus, is heavy, hard, compact, with very 

 minute, heavy pores, hardly visible to the eye. The microscope shows these pores 

 50 mic. in diameter, with thick walls 250 mic. (Fig. 601). This series only occurs 

 in the tropics and is unusual there. 



Fig. 601. Fig. 602. 



Section across the pores, ( X 12 ) 



The other series is light in weight compared with the preceding, we judge 

 about one-third as heavy. It has thin walled pores 120 mic. in diameter, with thin 

 walls, only 60 mic. (Fig. 602). It is the common and only series in temperate regions, 

 but is also common in the tropics. 



Most Fomes of this section Ganodermus do not have laccate crust, a character 

 that is prevalent in the section Ganodermus of Stipitate Polyporus. 



The color of the pore mouths has never been held of any importance in classify- 

 ing this group of plants. Still the difference between plants with white pore mouths 

 and those with yellow pore mouths seems to us of some importance. It is usually 

 constant in every specimen of the same collection. They are either all yellow or all 

 white. And it is also geographic. In Europe only one rare species, Fomes laccatus, 

 has yellow pore mouths, and it is a constant character of the species. In the Eastern 

 United States the commonest of all common species, Fomes leucophaeus, has white 

 pore mouths. On the Pacific Coast most specimens we received have yellowish 

 pore mouths, and in the tropics we get specimens with deep yellow pore mouths. 



SECTION 73. FOMES-GANODERMUS. 

 A. Pores with Thin Walls. Spores Smooth or Punctate. 



FOMES APPLANATUS. Pileus usually applanate, with a 

 brown, rather soft crust when fresh. Context color dark brown (bay 

 brown). Pores minute, with brown tissue and white mouths. Spores 

 colored, obovate, 6x10, truncate at base, with smooth, punctate 

 surface. 



This is a frequent species in Europe, and in various forms is cosmopolitan, 

 and usually the commonest Fomes in any locality. The type form in Europe has a 

 pileus often large, 1-1 > foot in diameter and 2 to 4 inches thick. It has a brown 

 crust, which in the growing plant is soft so that it can be indented with the finger- 

 nail. The pore mouths are white, and amateur artists often etch by cutting the 

 white surface, exposing the brown tissue beneath. Specimens of Fomes applanatus 

 (and the form Fomes leucophaeus) often have the pileus covered with a dense coat 

 .of brown spores. It is somewhat a mystery how they get there. That they are in 

 part conidial has been demonstrated by sectioning the pileus layers, and we have 

 seen abundant conidial spores attached to the hyphae. They are exactly the same 

 in every respect as the spores one finds in the pores. But that they alone can ac- 

 count for such abundant spores as one often observes is difficult to believe. 



The early history of Fomes applanatus is somewhat obscure. , Sowerby con- 

 fused it in the text with Fomes fomentarius, and Persoon first lists it as a variety 

 of Fomes fomentarius. Schweinitz determined the American form as being Fomes 





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