[Vol. 2 



690 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



P. fumosus. After considerable study the writer has decided 

 that to P. adustus should be referred those collections with a 

 thin, finely tomentose pileus, a thin, even margin, and minute 

 black pores. The species does not grow densely imbricate as 

 in P. crispus (see pi. 23 fig. 7) and does not have the crisped 

 margin of that species. The illustration of P. adustus given 

 by Patouillard 1 represents our plant very well. From P. 

 Burtii it is to be distinguished by the smaller and more equal 

 pores, the thinner, sterile margin of the pileus, and the firmer 

 context. It is much more abundant than the other three 

 species and frequently grows semi-resupinate. 



According to Fries, P. crispus differs from P. adustus in 

 having a thin, crisped, margin and large unequal pores. One 

 lot of segregates from my P. adustus material possesses just 

 those distinguishing characters, and I have, therefore, revived 

 the Friesian name and applied it to my plants. They are 

 certainly distinct from the specimens referred to P. adustus 

 though connected by intergrading forms to some extent. The 

 illustrations (pi. 23 figs. 7 and 8) show typical specimens of 

 the two species. 



I have seen no specimens other than the types that could be 

 referred to P. Burtii. The type specimens differ from the 

 above conception of P. adustus in having a somewhat thicker 

 context, a thicker margin that is fertile below, and larger and 

 more unequal pores. The hymenium is black, as in that 

 species, and the surface of the pileus is finely tomentose. The 

 flesh of the pileus is also very soft and almost floccose in 

 texture. It has been held by some that the mouths of the 

 tubes in P. adustus become larger and more irregular in ma- 

 ture plants, and if such a character stood alone in the differ- 

 entiation of these forms it probably should not be considered 

 a specific character. But it is the writer's opinion that in P. 

 adustus they do not become much larger in old plants, and 

 since P. Burtii differs also from that species in the other char- 

 acters mentioned above, we must consider it a valid species, 

 at least until other collections throw more light on the subject. 

 From P. crispus it may be separated by the fact that the 



1 Tab. Anal. Fung. f. 11,2. 



